I might very well be missing something here, but I will give this a try.
Both scene-referred (filmic) and scene-referred (sigmoid) are available options in preferences>processing. If I pick filmic then it is on by default when I load a photo into the darkroom. Sigmoid is on by default if I pick that option.
If I choose the option “none” I would have to pick “rgb scene” when working with masks.
How can I edit in a scene referred workflow whereby I can pick either filmic or sigmoid without having to turn one of them off should I choose the other and at the same time be in “rgb scene” when working with masks?