I'm having this issue with my Druid as well - trying to add a homebrewed creature as a Wild Shape for my Druid.  I've checked all my settings 5 or 6 times and was able to add a homebrewed cantrip, so it seems to just be a bug in the extras tab.  Hope it gets fixed soon, but the creature page itself is connecting to Beyond20, so at least I have a workaround for now!  :-)

Had the same issue mainly posting here so can see if any updates occur. Made a creature in homebrew it is unavailable through the extrass tab even though homebrew magic items are having no problem.

Quote from DxJxC >>

If your character knows find familiar, that spell makes a filter for familiars. You can toggle it off when adding to extras (there should be a checkbox).

If not, IDK post a link to your character and your private homebrew and a mod might be able to figure it out.

[Edit] Saw a second report and tested it. Homebrew monsters aren't working in extras right now.

 Okay thanks! it is good to know it is not just me! 

I am unable to see or select homebrew creatures in the extras menu even though I have selected to allow homebrew on each of my characters. 

I made a homebrew mouse to use as a pet for a character.  I used the rat as a template, changed the name to "mouse", tweaked some parameters and saved. 

When I go to add a pet and search for mouse, I can't find it. I have homebrew content enabled for the character, and I double checked the spelling.

I also can't find a magpie familiar that I created previously and added to another character a while ago. Even if I go into that character, which currently has the magpie listed as a familiar, I can't find either the mouse or the magpie when searching for a pet or familiar. Obviously I could find it when I added it to the character originally, so something strange is going on.

Any ideas?

There is currently a glitch with adding homebrewed monsters to a character sheet’s extras. The Devs and Mods are aware of it and are working on it. I hope this info was helpful.

Ah, thank you. Yes, I just wanted to make sure I wasn't doing something wrong.

Extra's are not appearing either 

Yeah there have been a couple of threads about this the devs have mentioned they are aware and working on this.

Home brew is toggled and I still can’t add it

I haven't seen a post about this topic in about a year and was hoping someone had more information about how to add a homebrew monster to the extra tab on a character sheet. Is this still not working or am I doing something wrong? I looked at their trello roadmap and didn't see any mention about trying to get this implemented (it could possibly fall into the "Character Builder Overhaul" or "Homebrew Revamp" but it's not mentioned specifically). Does anyone know if any dndbeyond employees have specifically said if they will add this feature?

It was implemented a long time ago, it’s just glitched currently. There have been several posts about it in the last two weeks.

For example: https://www.dndbeyond.com/forums/d-d-beyond-general/bugs-support/68651-cant-use-homebrew-monsters-in-extras

And: https://www.dndbeyond.com/forums/d-d-beyond-general/general-discussion/43305-how-do-you-add-a-homebrew-monster-to-the-extras

Please don’t repost this in those threads as it makes it more difficult for the Oath of Moderation Paladins to banish the Code Devils. I am only linking you so you know you’re not alone. 

It was implemented a long time ago, it’s just glitched currently. There have been several posts about it in the last two weeks.

For example: https://www.dndbeyond.com/forums/d-d-beyond-general/bugs-support/68651-cant-use-homebrew-monsters-in-extras

And: https://www.dndbeyond.com/forums/d-d-beyond-general/bugs-support/69355-adding-homebrew-pet-in-extra-tab

Please don’t repost this in those threads as it makes it more difficult for the Oath of Moderation Paladins to banish the Code Devils. I am only linking you so you know you’re not alone. 

Has this issue been resolved? I seem to have run into a similar scenario.

No,  it has not been fixed... Not sure what the issue is.  It would be nice to know an expected timeframe for a resolution to this issue.

Hello everyone! Thank you for your reports. This issue should now be resolved!

Currently just encountered this issue. The homebrew is tagged as misc currently but isn't showing up in any of the categories. Is there still issues or might i be doing something wrong?

Quote from Semaby >>

Currently just encountered this issue. The homebrew is tagged as misc currently but isn't showing up in any of the categories. Is there still issues or might i be doing something wrong?

 Is homebrew turned on for the character sheet?

Encountered this issue today myself. A character created last week with a homebrew Beast Companion works just fine, but today's does not show up. I am also not able to tag it as a Mount, which is what it should be under. I thought the issues was due to not having it "published" like my one was last week, but after publishing it, it still does not show up.

Still occurring end of November! :o

nevermind it works, haha