Interesting thread. Thanks all for the input.
Slightly off topic, but in a way it might help others somewhat: the way I work with setups is before I hit the track, I will create a base setup in GPLSM (if I don't have setups for that car/track combo) based on previous experiences of other cars/mods, or based on other track setups with about the same characteristics. Or using setups from aliens, and tweaking them to my hardware settings and driving style. You have to have some theoretical setup knowledge and know what you're doing. Most of the time this method works well for me having a pretty good base that doesn't need major tweaks while testing the first time. Mostly subtle tirepressure and camber changes, or balance (roll).
I will load the setups in GEM, so the right setups are loaded when entering the game. For most tracks/car combo's the latest used setups are loaded correctly for quali and race.
In short, I only use custom setups in the players/...../setups/tracks folders, either making one from scratch based on experience/knowledge, and then saving it in the respective players/...../setups/tracks folder. I load them in GEM.
Happy New year all!