Ok guys, I have a workaround:
-Install a mod (any one of them, just need to unlock the mods menu)
-Open the mod menu after launching the game
-If you want to keep global leaderboard enabled, don’t select any mods.
-Launch your desired level
-???
-Profit
This keeps your progress saved in the game as if you were using the regular campaign mode, so there’s really no difference except a few extra steps in launching the level.