99% of my music is classical. For proper organization Id like to sort by opus numbers as well. In dBpoweramp Ive included this custom tag already when ripping. How to tell asset in Linux (CentOS 7.3) to index for this custom field?

Another question is related to custom tags in PerfectTUNES (PT) (Im running this on a windows 10 x64 machine). How to install custom tags in PT? Maybe Id better open a new thread in PerfectTunes for this?
Heres what I tried so far: ...\AppData\Roaming\PerfectTunes:
1) file "DefaultTagEdit.txt": adding new line "Opus" at the end
2) file "IDTagDatabaseFields.txt": adding new line "Opus,0,NVARCHAR(30)" at the end

Best regards