Hi there,
Well, one way, you can always filter any type of file in the library viewer using title formatting. You did not mention which UI / library viewer you are using?
It might be more effective with a tree style library viewer (Album List, Library Tree), seeing you can have a top level branch for each type ("CUE Files" / "Media Files"). With a column style library viewer (Facets, Columns UI), you could use tabs for each type with a second library viewer instance under each tab. I guess the usefulness of that depends on your layout. (Or mix both, use tabs with trees)
For example, if using Album List, putting this at the beginning of any view pattern (Preferences > Media Library > Album List) should divide the top branch into the two types -
$if($stricmp($ext(%filename_ext%),cue),CUE Files,Media Files)|
(Not that I've tested this specifically with CUE files because I do not have any )
If using Facets, that has a built in filter button that uses query syntax. You could toggle either type using that button drop menu (Preferences > Media Library > Facets > Filters) -
"CUE Files"
"$stricmp($ext(%filename_ext%),cue)" PRESENT
"Media Files"
"$stricmp($ext(%filename_ext%),cue)" MISSING
Alternatively with column library viewers, have a filter column for extension / codec that includes CUE Files -
$if($stricmp($ext(%filename_ext%),cue),CUE,$upper(%codec%))
I guess another way would be to just use playlist grouping. You could add the above extension / codec code to the grouping, so when selecting in the library, the playlist would show the same album in two separate groups if both are present - one for "CUE", one for "FLAC". (Probably not ideal...)
Cheers