It looks like "Custom Group' and 'Custom Category' are the same thing, then there is 'Custom' and 'Custom 2' which are something else I think. The first two should use the same terminology and the second pair should be described/explained somewhere, I think they are used in the title caption and edit function.
I will switch "Custom Category" to "Custom Group" to be consistent. Custom and Custom 2 are just text fields that accept any input you want to provide. It can be used with the title formatting or with filtering (you can search based on the custom fields).
Thanks,
Mike
The same happened in the German translation. Whereas it is "benutzerdefinierte Gruppe" (Custom Group) in most cases, the settings screen refers to it as "benutzerdefinierte Kategorie" (Custom Category). I'll send you an e-mail, hopefully by Sunday, with the exact German wording.
And I came across another inconsistency regarding "type" / "source" / "source type".
The point is that some terms show up several times: in the tab header of the library, as a field text in the song editor, on the settings screen, in the "configure fields" window, in error messages and there might even be more places. It's confusing for the user if the wording is not exactly identical