Feature Request

I confirm:

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

Description

On Linux, Proton, whenever a Steam Windows software, a .exe or .msi file is played the 1st time, a new steamapps/compatdata/a_number folder with inside a new Proton prefix is created.

But it's possible to have Windows softwares in a single Proton Prefix, as Wine.
The key is:
LAUNCH OPTIONS: STEAM_COMPAT_DATA_PATH=proton_prefix_path %command%

I wrote a guide https://steamcommunity.com/sharedfiles/filedetails/?id=3378517770 about this.

But this option must be written for each Windows softwares, so to avoid this, the feature request:
the single Proton prefix by default, or as option in general (e.g. in Settings, Compatibility, checkbox Single Proton prefix) with the choice of the Proton prefix path.