One of the required fields when making a spell is for which class gets the spell - I understand why, it's for sorting and searching.

My question is thus: How do I create a spell that will not show up in any character's spell list, as it's only for use on an item?  Is there a flag somewhere to say "Do not allow a character to choose this spell" that I'm not aware of?

D&D 5th Edition rules and therefore D&D Beyond doesn't support spells that cannot be cast normally. Because that's what a spell is.

A spell-like effect caused by a magic item that is not a spell that can be cast normally isn't a spell, it's just a function of a magic item.

Cyb3r is correct. You can however make a homebrewed Barbarian subclass with “can cast spells” set to “yes” and a class feature named “Spellcasting” and nothing else and then you can designate that subclass as the only “spell list” upon a spell appears. That will let you make a spell that does not appear on any actual spell list.

I hope that helps.

Hmm.  Okay.

It would be nice to have spells specifically for items and/or monsters to use, but not players. 

I'll have to work around it, I suppose. Thanks!

Quote from IamSposta >>

Cyb3r is correct. You can however make a homebrewed Barbarian subclass with “can cast spells” set to “yes” and a class feature named “Spellcasting” and nothing else and then you can designate that subclass as the only “spell list” upon a spell appears. That will let you make a spell that does not appear on any actual spell list.

I hope that helps.

 Single most helpful thing I have found on a forum in ages. Thank you.