I've read someplace that the subtle pre-loaded "play" I feel in the large shift lever [as opposed to the smaller "dump" lever. . .or do I have that bass-ackwards?] is to invoke some sort of small tweak on the derailleur throw.

Could some kind person 'splain this to me? How would I know when I need to toggle it? Noise in the drivetrain maybe? Is there something here I need to consider when adjusting the derailleurs? Does it apply to both fore and aft derailleurs?

Mercy buckets. . .