Mp3tag v3.19 was from 2023-01-27, two and a half year ago.
We are currently at v3.30d, 10 main versions and many subversions of Mp3tag later.
I would say this is highly subjectiv.
Ctrl + O for Options, 1 mouse-click on the "Tag Panel" entry, 1 double mouse-click on GENRE and 1 mouse-click on the Manage-Button to manage custom list values is not really "buried somehwere" IMHO.