You might want to join FEUcord for prompt help 'cause most of the wizards aren’t particularly active on the forums.
I know Snakey did work on custom prep screen, as they made base convos for Legends of Avenir. Their ASM thread:
I’m like 100% certain there’s newer, easier to use stuff to remove entries from preps, but I’m also pretty sure it’s not available on FEB patches yet.