I don't know if UserTracks should be classed as Abandonware ??
I wanted to try swapping a RealTrack with a user track like here
Home Made Flamenco Realtracks

I thought I could do it with this one Guitar, Acoustic, Strumming AcRockBright Ev 120.zip as it has A B parts, holds and you could change the hold number to your usertrack holds, as you can copy the holds folder, rename the hold files and replace the audio with yours, see
Good Ear Needed

I got Holds-67 to work as a new custom hold by renaming all the wav to SH867x.wav and renaming the references in Holds_867.xm2 then I set the RealTrack to that hold in Soloist > Soloist Maker Edit > More and it all seemed to work.
The holds have something along these lines: C Cm C7 CMaj7 Cm7 Cm7b5 Csus4 C7sus Caug Cm7#5