Assume there's some mild quirks to this; when deep it'll need winding in (as the IP will be much higher than when shallow).with the clicky ones you can typically just remember the number of clicks from "off" that you need for deco and then adjust as your ppO2 starts driving. Drifting up, turn it back a click, drifting down then turn it up a click. If you have a blocked first stage then it is not depth dependent, just workload dependent and the Fathom uses this approach albeit without a clicky needle. When you have a normal needle, the process is the same just without the detents to tell you where it is located.
Do like the click concept; that would seem easy enough to twiddle.
Don't suppose you have a link to an example?
Would be great if the Revo had this on the excellent injection block.