It is even worse. Enpass shows only a fixed amount of custom icons (icons you uploaded manually to the database), so you are not able to delete icons, which don't show up in the list. Currently, I see 74 custom icons (out of over than 100). If you want to select a not visible icon, you have only the chance either to copy an entry, where it is used or to upload it again.
I already reported this error repeatedly to Enpass, but it is still not corrected.