Why is it that the DM can modify/edit all of my my sheet? I can understand the need to view it, though the part of my notes is questionable.
Even when I am Signed Out, this is possible. Is that correct? Why are editing rights not blocked? 
I feel I should be the only one capable of full editing my character sheet.

DM should be able to see everything.  Ours has even corrected stuff we put in wrong.  

It's a disussion to have with your DM. I think it's common and useful for the DM to have full access to it. This allows them to incorporate your character better into the story. For example, I frequently check the background and appearance sections of characters for campaigns I run so I can properly set up scenes. These are normally hidden.

As for editing your sheet, I think it's better to ask the player to change something rather than doing it yourself as a DM.

If you want the notes to be invisible and editing to be limited to you, don't put your character into a campaign.

Quote from The_Crycket >>

DM should be able to see everything.  Ours has even corrected stuff we put in wrong.  

 To see yes, but changing of Name, Race, Class, Alignment etc are not  needed in IMHO 

Sometimes it's handy since it means that I can change things for players who are struggling.

Obviously tastes vary by table, but I've always believed in everything being open. The players can see what each other's characters are. The one time I didn't insist on this, the guy ended up cheating and wrecking the game until I cottoned on to what was happening. Again, if I'd had access to his sheets, that investigation would have gone quicker.

Ideally, even players would be able to edit each other's sheets. Why not? We can all help each other. Unfortunately, that's a bit too idealistic and so we don't allow that. The DM having that ability is a matter of convenience, and to be honest if he's screwing with by editing your sheet in a bad way (changing the name without permission, trolling etc) then your game is screwed anyway and you'll be glad that you found out and left when it only reached the level of messing with character sheets rather than worse stuff.

I'm in favour of full access myself. In the games I've played in it's always been a nice surprise when the DM pulls a story beat or sets something up to play to a cool feature I have that I wasn't expecting. In the games where I DM I've either normally got beginners, who benefit from me checking they've not forgotten stuff when they level up, or really experienced people playing homebrew or 3PP subclasses and it helps me to know what features they'll have

What Linklite said

Also, the DM can change your sheets because the DM can change your character in-game. Perhaps ideally, some things would be protected, but DDB doesn't have granular access control, and it's not that big a deal in practice, because if you can't trust the DM, your game is broken anyway.

Full Access - there's no reason you can't keep additional notes elsewhere, but as a DM it's super useful to have all the characters in a party in the same place.
Sometimes (as DM) I might want to better clarify some things, place/NPC names - stuff like that + I'll just do it + PM the player on Discord about the changes I've made + that's just to reinforce the players familiarity with the setting.

I've seen Level 1 characters that have been "welcomed to the party" and all of a sudden they've got a +3 Sword in the first session.

D&D's a social game, if the DM/players are messing with the sheet unreasonably* it's down to those involved to decide if that's the game for them.

*little more than opinion, but you shouldn't be playing a game with people that you don't enjoy playing with.  It's down to interpretation, personal choice etc. etc.

If you were playing pencil and paper in person, it's generally custom for a DM to be able to review a players' sheet, and the table, not just the DM, would be wary of someone who refused.  The DDB campaign set up is reflective of this practice. Players shouldn't have secrets from the DM.  While the DM plays the adversaries (among many other roles) the dynamic of the game between DM and player is not adversarial, and hiding play material from the DM really only leads to dissonance and compromising the DM's ability to facilitate a fun game.  There's also a simple solution to prevent a DM from reviewing your notes, take notes on something other than your character sheet.  While again it's accepted custom, and arguably a necessary custom, to entitle DM/GMs to reviewing a character sheet, examining scratch paper or other docs would be considered excessive if the player didn't invite it.  

I would say DM access to player notes and journaling would actually benefit the player in that, with that knowledge that the DM can get about the player's game experience in those notes/journals, the DM can better shape the game to the player's interests.  

Quote from Some_Body_Else >>

Quote from The_Crycket >>

DM should be able to see everything.  Ours has even corrected stuff we put in wrong.  

 To see yes, but changing of Name, Race, Class, Alignment etc are not  needed in IMHO 

 A player should be extending some measure of trust that the DM is not going to make changes that are malicious. Sometimes it is actually necessary for the DM to make edits to a player's sheet and even notes. As a DM, I usually ask the player to make changes themselves but if that is not done for any number of reasons (I have a very absent minded player), I might just make the changes myself to save me the exhausting process of repeatedly asking them to change it.

Assuming they are not making malicious changes, a DM should be able to see and change what they need to. If the trust is there and theres a valid reason to even change the class, then so be it. But thats something that should be talked about before hand.

If your DM is changing things without the players consent, that is an issue that goes beyond what permissions DDB grants DMs; that's a table problem. IMO every issue that could be caused by the DM having full access to a characters sheet would be a symptom of a larger issue and not one in and of itself. Conversely, that lack of access would cause more issues in preventing DMs to effectively help their players manage their sheets. It's a Risk/Reward thing; Risk is low, Reward is high.

As for hiding information from the DM, that seems to assume a player/DM dynamic that the game doesn't really support. The DM is not supposed to be placed in opposition to the players, they are an enabler of the players enjoyment. Anything you hide from your DM is something your DM cannot enable to happen in the game. 

DM should have access to everything. I can see an argument for notes, but just keep them separate.

I am also on board with the DM having full access to the sheet.  As stated, a DM making changes that you don't agree to is a little off, but that is a table issue, not a DDB issue.  I think the number of DMs who would "abuse" such power is low, so shouldn't be a big issue for MOST folks out there,

So far as notes or other secrets you try to hide from the DM, well, again, that's a table issue and a sign, to ME at least, that you may not be entirely on board with D&D as a collaborative storytelling game.  Hiding things from the DM (and to an extent DM hiding TOO much from the players) isn't a good atmosphere.  Sure, a decent amount of stuff has to be DM controlled and kept under wraps, but anything they intend to DO to your character needs to be out in the open, at least between that player and the DM.

All boils down to trust, and if you absolutely cannot trust your DM, it may be time to seek a different table.

Having access so that the DM can incorporate backstory or features into the game is fine.

If a player is struggling and the DM can see what is wrong, explaining why or how something works I think is better than just taking the sheet and fixing it yourself.

DM’s and Players should be working together if there are issues. Communication is a key part of the social contract and the DM isn’t above this. 

An example, not quite the same but appropriate, I think, is with my Druid. As part of the campaign I became linked to a grove via a seed, where upon my death I would become the “father tree” of that grove to keep it flourishing. Unbeknownst to me (as the player) the seed that linked me was stolen by another player and the DM allowed it completely outside of gameplay. That player eventually left the campaign but it was many months before I found out what happened during out of character discussion with the group. I was a little pissed to say the least but I didn’t say anything. I can roll with it. To my point: If this was something that the player wanted to do, I think the player, DM, and myself should have discussed this and I probably would have been fine RPing the situation and playing it up. Player knowledge isn’t the same as character knowledge. But all agency was taken away from me in this situation and I feel the same can be said for a DM just changing character sheets instead of working with the player if changes need to be made. 

Quote from Falwith >>

I am also on board with the DM having full access to the sheet.  As stated, a DM making changes that you don't agree to is a little off, but that is a table issue, not a DDB issue.  I think the number of DMs who would "abuse" such power is low, so shouldn't be a big issue for MOST folks out there,

So far as notes or other secrets you try to hide from the DM, well, again, that's a table issue and a sign, to ME at least, that you may not be entirely on board with D&D as a collaborative storytelling game.  Hiding things from the DM (and to an extent DM hiding TOO much from the players) isn't a good atmosphere.  Sure, a decent amount of stuff has to be DM controlled and kept under wraps, but anything they intend to DO to your character needs to be out in the open, at least between that player and the DM.

All boils down to trust, and if you absolutely cannot trust your DM, it may be time to seek a different table.

 I agree with you that it’s more of a table issue and less a DDB issue. But DDB is a tool and if the tool isn’t doing what it could to help eliminate an issue I think it’s fair to bring it up. 

Alignment change by the DM is definitely needed if you veer into a different alignment and there's some mechanic that uses it in the game you're playing. (Example: Evil characters in Descent into Avernus don't have to worry about a mechanic that Good and Neutral do.) 

And if your character has been pickpocketed the DM needs to be able to take (or add if it's a generous plantpocket) as needed. 

GMs should have full access to character sheets - all of it. They should also be allowed the make edits. This is with the understanding that the GM is following the social contract just like they are expecting the same from their players. 

I've done edits on exp, hp (during combat), class and level upon resurrection, being the host for slaad or xenomorph, keeping track of backstory so I can incorporate it into the campaign, all manner of things because the players are new to DDB and don't know how to do it.

The big one for me is cursed items or items that level up with the character.

Quote from Rathkryn >>

Alignment change by the DM is definitely needed if you veer into a different alignment and there's some mechanic that uses it in the game you're playing. (Example: Evil characters in Descent into Avernus don't have to worry about a mechanic that Good and Neutral do.) 

And if your character has been pickpocketed the DM needs to be able to take (or add if it's a generous plantpocket) as needed. 

 I disagree. If an alignment change is needed the DM should talk to the player and the player should change the alignment on the sheet. 

As far as pickpocketing, what better way to let a player know they were pickpocketed then an item magically disappearing off their sheet. I, as DM, would just keep a mental (or physical) note and when the PC looked for the item then would tell them. Personally, I wouldn’t have an NPC pickpocket a PC. But if it’s important to the adventure for the attempt then sure.

If I remember correctly when I ran the Lost Tomb of Martek back in AD&D, an NPC party met the PC party and it was written in the module that an item was stolen from the PCs which then lead to a chase through parts of the module. 

Quote from Wysperra >>

GMs should have full access to character sheets - all of it. They should also be allowed the make edits. This is with the understanding that the GM is following the social contract just like they are expecting the same from their players. 

I've done edits on exp, hp (during combat), class and level upon resurrection, being the host for slaad or xenomorph, keeping track of backstory so I can incorporate it into the campaign, all manner of things because the players are new to DDB and don't know how to do it.

The big one for me is cursed items or items that level up with the character.

 First, give a man to fish they eat for a day. Teach a man to fish they eat for a lifetime. Why not use the opportunity to teach the new players how to actually do things. 

And second, I completely disagree. If you need something edited on a character sheet you talk to the player and have them make the changes. Isn’t that part of the social contract? Working together?