I am trying to make some updates to homebrew monsters to use the 2024 versions of a few spells (because I like some of them), yet I can't get them to work right. I am not sure if I am not putting in the right scr, or if this isn't yet applicable to spells. I would hope it will be in the future. 

If anyone has a solution for it now, it would be greatly appreciated and be a big help.

https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/131411-a-homebrewers-how-to-faq#GeneralHomebrewFAQ&BasicTroubleshooting
Just use the link above, it helps. 

Okay, folks, after a couple of quick checks and double-checking of how things work. I found two things to help anyone else with this issue. 

https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/9811-how-to-add-tooltips

This helps with how tooltips work, big help here. Great Thread.

Now for the new stuff, it can be done by typing spellsrc=free-rules or spellsrc=phb-2024 which will grant the latest versions of the spells. This is also true for probably new monsters. Follow the threat above when the new Monster Manual and DM's guide come out, as those sources will let you have the new items/monsters tooltips work too.

I hope this can now help many others as it has helped me. 

If you check the General Homebrew FAQ, question #4, all the way at the bottom of that answer you can find a link to a post listing all the updated 2024 tooltips: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/131411-a-homebrewers-how-to-faq#GeneralHomebrewFAQ&BasicTroubleshooting).

THANK YOU, this is also a big help. As an avid monster maker, this will be very helpful.

all my spells in my homebrew monsters point to the 2014 spells is there a workaround to point to 2024 spells? @cartertheKing - you mention spellsrc=phb-2024 but where do I put this?

Quote from mwalkerhall >>

all my spells in my homebrew monsters point to the 2014 spells is there a workaround to point to 2024 spells? @cartertheKing - you mention spellsrc=phb-2024 but where do I put this?

 
See Post 3 above. It has your answer.

*psst….* 👇

Quote from Cyb3rM1nd_Test >>

Quote from mwalkerhall >>

all my spells in my homebrew monsters point to the 2014 spells is there a workaround to point to 2024 spells? @cartertheKing - you mention spellsrc=phb-2024 but where do I put this?

 
See Post 3 above. It has your answer.

They’re 👆 right.

Yes, that form has some answers, but for a quick guide, put the src tag in the first tooltip bracket, behind whatever it is your using. So [spellsrc=phb2024] and than do the normal end tooltip bracket.

Quote from CartertheKing >>

Yes, that form has some answers, but for a quick guide, put the src tag in the first tooltip bracket, behind whatever it is your using. So [spellsrc=phb2024] and than do the normal end tooltip bracket.

 
[ spellsrc=phb2024 ]Cure Wounds[ /spell] = Cure Wounds

[ spellsrc=phb2024 ]Cure Wounds[ /spells] = Cure Wounds

-

[ spells ]Cure Wound[ /spells] = Cure Wounds

-

I think I will stick to the guide Sposta linked to. Much easier and faster.

Do so, just trying to be helpful.

Same, and the point is that "src" isn't the proper way the system identifies the tooltips. You'll note the first tooltip I did with your src method actually produces the wrong tooltip.This is because it is actually ignoring the src bit and going off the tags being spells instead of spell. So, you're actually misinforming people unintentionally.

So, I'm just clarifying the guide is better, because it's, well, correct first off and also more efficient and gives all the info.

Replying to this cause I still had trouble figuring out. With spells at least, the tooltip defaults to the 2014 rules, to use the new 2024 version, type "[ spellsrc=free-rules ]Fireball[/spell]", without spaces in the brackets. I've confirmed this updated my homebrew magic item tooltips, you can also use "spellsrc=phb-2024", however, some spells seem work with one or the other. I noticed that at least the spell "Otiluke's Freezing Sphere" had issues with "phb-2024" yet worked with "free-rules" while other spells seem to prefer "free-rules". The "spellsrc=free-rules" seems much more reliable but some spells have issues with it, anyone else notice any wonkiness like this? I've also noticed these src tooltips really don't like copy and paste, I've had 10 spells on an item before, got the first one to work via "spellsrc=free-rules", and after saving & checking, i'll copy that text & past it into other spell snippet brackets, and beyond won't even recognize them as tooltips until I re-type them, bolding the brackets seems to cause the same type of issue.

Use these examples with NO SPACES in the brackets, fireball preferes "free-rules"
[ spellsrc=free-rules ]Fireball[ /spell] = Fireball
[ spellsrc=phb-2024 ]Fireball[ /spell] = Fireball
[ spell ]Fireball[ /spell] = Fireball

Banishing smite only works phb-2024 for some reason
[ spellsrc=free-rules ]Banishing Smite[ /spell] = Banishing Smite
[ spellsrc=phb-2024 ]Banishing Smite[ /spell] = Banishing Smite

Otiluke's Freezing Sphere

Otiluke's Freezing Sphere

Quote from JerrodTheShadow >>

Replying to this cause I still had trouble figureing out. With spells at least, the tooltip defaults to the 2014 rules, to use the new 2024 version, type "Fireball", i've confirmed this updated my homebrew magic item tooltips. However, some spells seem to not work with this for whatever reason. I noticed that at least the spell "Otiluke's Freezing Sphere" had issues and I couldn't get it to point to the new version, so it may still be a little wonky. I double checked that there is a 2014 & 2024 version of this spell, even tried just calling it Freezing Sphere, no luck. Anyone else notice any wonkiness?

 
Nope. Works fine for me. Although for spells with ' in them I'd ensure you paste without formatting because sometimes fonts change the ' to a different type the tag system won't recognise.

Quote from JerrodTheShadow >>

Replying to this cause I still had trouble figuring out. With spells at least, the tooltip defaults to the 2014 rules, to use the new 2024 version, type "[ spellsrc=free-rules ]Fireball[/spell]", without spaces in the brackets. I've confirmed this updated my homebrew magic item tooltips, you can also use "spellsrc=phb-2024", however, some spells seem work with one or the other. I noticed that at least the spell "Otiluke's Freezing Sphere" had issues with "phb-2024" yet worked with "free-rules" while other spells seem to prefer "free-rules". The "spellsrc=free-rules" seems much more reliable but some spells have issues with it, anyone else notice any wonkiness like this? I've also noticed these src tooltips really don't like copy and paste, I've had 10 spells on an item before, got the first one to work via "spellsrc=free-rules", and after saving & checking, i'll copy that text & past it into other spell snippet brackets, and beyond won't even recognize them as tooltips until I re-type them, bolding the brackets seems to cause the same type of issue.

Use these examples with NO SPACES in the brackets, fireball preferes "free-rules"
[ spellsrc=free-rules ]Fireball[ /spell] = Fireball
[ spellsrc=phb-2024 ]Fireball[ /spell] = Fireball
[ spell ]Fireball[ /spell] = Fireball

Banishing smite only works phb-2024 for some reason
[ spellsrc=free-rules ]Banishing Smite[ /spell] = Banishing Smite
[ spellsrc=phb-2024 ]Banishing Smite[ /spell] = Banishing Smite

 
Yeah, you're using the src thing which, as already mentioned, doesn't work properly. Please see Post 3 for a link to a guide that shows how to do the tooltips properly.