[Feature Request] Resolution Configuration/Configuration Selection

I think it would be an awesome idea for systems with multiple states to select between them without third party tools.

I envision a few new steps during startup for my feature request:

1): On loading the main configuration (retroarch.cfg), check if a flag is set that allows chaining configurations.

2): If chaining is allowed according to the above referenced flag, check if a configuration file specific to the current maximum allowed resolution (retroarch-1920x1080.cfg) is available as an override.

3): On loading the main configuration (retroarch.cfg) and any targeted resolution configuration (retroarch-1280x720.cfg), check if a label is set for a configuration prefix (zsv) which will mark certain files for selected chaining.

4): If a configuration prefix (kse) is set according to the above referenced label, show a popup allowing the user to select between configurations (mobile/docked) on startup which will then load a related (retroarch-kse-mobile.cfg/retroarch-kse-docked.cfg) file.

I believe such a feature would dramatically reduce the requirement for third-party tools for any users with portable devices, like the Steam Deck, which are on the rise.

Please imagine a device that has different performance characteristics, for example, depending on whether powered by a battery or mains; the selection of chaining as referenced in this feature request could easily be setup so that a user could automatically activate shaders if powered by mains or deactivate shaders if on battery.

Start by tracing how startup loads retroarch.cfg and whether resolution-specific files such as retroarch-1920x1080.cfg are handled. Review the proposed prefix files, including retroarch-kse-mobile.cfg and retroarch-kse-docked.cfg; done would require an agreed design and working configuration selection and chaining across the described cases.