Expose Linux Steam's process & API from within Proton for stuff like ModOrganizer

Feature Request

I confirm:

• that I haven't found another request for this feature.
• that I have checked whether there are updates for my system available that
  contain this feature already.

Description

Running Skyrim with ModOrganizer in Proton is almost possible, by putting ModOrganizer (its EXE and associated files) in Skyrim's root folder, and symlinking SkyrimLauncher.exe -> ModOrganizer.exe. There's just one last obstacle: ModOrganizer, while running under Proton, cannot see or interact with the Linux client of Steam.

I would assume it's checking for a Steam.exe process, and then possibly using Steam API URLs, such as steam://rungameid, to run binaries. Is it possible to make WINE applications see a Steam.exe process that's actually just pointing to the Linux client process? If so, is it also possible for WINE to open those URLs natively in Linux, so that the Linux client would interpret them?

The issue names no files, tests, or entry points. Research how Proton/Wine could expose the Linux Steam process and route steam:// URLs to the native Steam client; done would mean ModOrganizer can detect Steam and launch those URLs successfully.