I just went in and moved my Original Works - Low Fantasy nominations to a new fandom slot, renaming the fandom slot that my Original Works - Post-Apocalyptic nominations stayed in from "Original Works" accordingly. And it gave me this:

Sorry! We couldn't save this tag set nomination because:

Someone else has already nominated the tag Original Character(s) (Original Work - Low Fantasy) for this set but in fandom Original Work. (All nominations have to be unique for the approval process to work.) Try making your nomination more specific, for instance tacking on (Original Work - Low Fantasy).
Someone else has already nominated the tag Any or No Characters (Original Work - Low Fantasy) for this set but in fandom Original Work. (All nominations have to be unique for the approval process to work.) Try making your nomination more specific, for instance tacking on (Original Work - Low Fantasy).
Someone else has already nominated the tag WB: Disability & Accessibility (Original Work - Low Fantasy) for this set but in fandom Original Work. (All nominations have to be unique for the approval process to work.) Try making your nomination more specific, for instance tacking on (Original Work - Low Fantasy).

YEP I SURE DID. you will notice I am not doing that anymore.

(those three tags are currently disambiged as "Original Work - LF"; sorry, mod!)