I also use multiple profiles. My setup is as fallows.
firefox -ProfileManager
Create 2 profiles work and private.Change the theme of work to orange and private to black.
Create two .desktop files and append to the Exec line -P work (or private) and the Name to include (work)
I have work on desktop 5 and private on desktop 8 and 9.
Works like a charme for me. Additional bonus. Use container to add additional seperation.