Even though not optimal to create a crossfade non stop medley it is perfectly doable on stagetraxx if you spend some time. But setting in / out points and speed effects the file in general and it would be optimal if each playlist had its own settings for a file.
Playlist separate in / out points , speed etc.
You could duplicate a song: https://stagetraxx.com/user-guide/songs/#duplicate-a-song and adjust the settings on the duplicate. Song properties will never be playlist specific.