Trying to make a Homebrew Feat that adds either a spell known, or adds a spell to one's spell list. However, can't seem to do that without either making said spell once a day. Any way to add a spell to spell known/spell list?

Does it have to add a specific Spell? There might just be a way to +1 to the character’s Spells Known. That wouldn’t help Wizards, but you just give them the scroll and leave it up to them anyway. If you’re adding a specific Spell I believe it either has to be #/day or Charges.

I tried this a while back and couldn't figure out how to do it. You CAN do it from a subclass feature; the subclass add spell options are more robust than the feat options, for some reason. If someone knows some workaround to actually imitate this behavior from a feat rather than a subclass, I'd love to hear it.

Quote from SagaTympana >>

I tried this a while back and couldn't figure out how to do it. You CAN do it from a subclass feature; the subclass add spell options are more robust than the feat options, for some reason. If someone knows some workaround to actually imitate this behavior from a feat rather than a subclass, I'd love to hear it.

 Ditto 

You cannot add to Class spells using anything except a subclass.

This is the reason Spells of the Mark feature for the new Eberron races doesn't work yet. Even the devs can't get it to work yet.