Missing Settings from the Permissions Section that are present in third-party tools (Flatseal)

Problem

There are a few tweaks to permissions like allowing access to external drives for Steam or applying environment variables to apps that can only be done via the command line or through a third-party tool called Flatseal from Flathub.

Proposal

I think that a some sort of text field should be added beneath the Home/Root folder toggle to be able to specify the directory to the external drives. And for environment variables, a separate section could be added at the bottom with text fields and stuff.

Prior Art (Optional)

Filesystem access

Settings for environment variables