Dave, I tried to suggest name changes for Japanese Wisteria (Wisteria floribunda 'Shiro Noda') to the accepted names and synonyms as in the RHS but the system told me the plant already exists.
Name: Evan Pioneer Valley south, MA, USA (Zone 6a)
Janet,
Is this the other in question?
I've come across this frequently. Delete one plant that "already exists" or the plant with the fewest pictures, data, ... that need to be moved. Then edit data accordingly on the one that remains. Don't forget to propose pictures be moved before you propose the delete. I'm guilty of this but trying to remember.