If you add a homebrew spell to your Collection but all of a character's spells are already known/prepared/chosen, the added (new) spell won't show up in the "add spells" list until you manually "REMOVE" a spell from your known/prepared spells, refresh the page, and open the "manage spells> add spells" list again. 

I have been racking my brain about this for almost an hour, trying to make the spell appear in the list. I went so far as deleting my browser's history and cookies... to no avail.

Finally found the issue, but there must be a possible fix for this.