I made a dungeon for around level 5 PCs and tested - which gave me a rando 1st level group. Who got TPK in the first encounter (as expected). I tried loading it up from the main screen planning on using my level 10 party I just finished the game with. However they show up for selection as their level 1 starting versions. I didn't select them anyway and see if it was a bug and I would get the level 10s.
Anyway - for those that have loaded other content can you select non level 1 characters and is it possible to test without getting a rando level 1 group?