Yea, it is a very round-about way.

1. Open the title screen settings and navigate to superb survivors

2. Enable superb survivors's debug mode and save settings. Remember to save settings, or it will reset to default.

3. Load your save file, and lure your companion into a bathroom

4. Ensure no hostile raiders or zombies are nearby. YOU CANNOT MOVE OR ATTACK WHILE IN DEBUG MODE

5. right click companion and select DEBUG - swap character

6. You are now the companion

7. Select the shower/tub/sink and wash yourself or use a cheating mod like Cheat Rebirth to skip all that and clean yourself direct from the cheat menu

8. You can also DEBUG yourself to add and remove traits post-character select. If you have a cheating mod, like Cheat rebirth, you can also change your stats.

I have not figured out how to change hair and face. Enjoy