Programs run through protontricks don't seem to have access to game directories

Hi there - I'm trying to get Skyrim SSE set up with Mod Organizer in protontricks. However, when using Explorer in prontricks to set the path to the game, I discovered that it wasn't mounted anywhere (as far as I can tell). I couldn't manager to navigate to my steam folder and point MO to my Skyrim directory.

I'm using the Steam flatpak and the protontricks flatpak. Filesystem permissions have not been modified from the defaults, so `~/.var/app/com.valvesoftware.Steam` access remains.