I read there's some research on Lion's mane, and there's a lot about caffeine and theanine but none of this are magic productivity pills. Like it's not that the concentration and productivity effects are obvious and reproducible among all humans. Caffeine has the "keep you awake thing" that cocaine also has and it's pretty reproducible but in most studies I've read about caffeine and L-theanine the flowy non-jittery productive state or any cognitive enhancement are spotty.

I think the other problem with cannabis as a workday desk-job productivity enhancement substance that you are not mentioning is its interaction with other drugs and the unpredictable and really deep tolerance buildup. Like giving an average someone a curve of how much they need to smoke to get the same "effect" among weeks or months is probably really hard.