Hi Dom- I have a better way to ask my question maybe. Can you tell me what is going on with this old-school setup? I have 2 (working, single pole) switches powered by 1, 3-wire cable. They are connected by a ‘jumper’ piece of wire. One switch is using the red wire and the jumper. The second switch is using the black, white and the jumper piece. (There is no ground.) How does the jumper pass hot current between the two? Can one switch be replaced with a dimmer (again still single-pole)?

Thank you!