When making a subclass using the homebrew tools here hoe does one make a subclass that has a spell casting ability for a class that doesn't normally have that option? I'm attempting to build a barbarian subclass with some magic casting abilities but I can't seem to give it the spell casting trait that unlocks the spell list menu in the character builder.

Please see the Homebrew Subclasses & Species FAQ #7: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/131411-a-homebrewers-how-to-faq).

That's so rude, all I was missing was the spellcasting thing... that's weird that you have to have that in there...

How was I rude?!? I politely directed you to a resource that held the answer to your question, as well is a slew of other helpful tips for future reference. I was trying to help. I even said “please” and everything just like mama taught me to do.

You have to have a spellcasting ability selected, a spell list selected, and sometimes you need specific phrases in the feature description to activate spellcasting in the character builder. Also btw Sposta’s post isn’t rude at all.

Quote from ImagineDragons289 >>

…Also btw Sposta’s post isn’t rude at all.

 
Well, I mean, I can be. Lord knows I can be rude, but I wasn’t trying to be this time. 🤷‍♂️

No no no, YOU weren't rude, the system is rude lol

Oh, okay. That makes more sense then.