I don’t often wave a driver past, but will if its a narrow road and can see its clear/a good spot stop pedalling, stand, and tuck in a bit. For me this has often worked as a clear sign that I think now is a good time for you to pass if you want to.
Also give the the thank you wave with the right hand, and a nod of the head by way of expressing appreciation for their consideration.
As a driver there are often times I’m a bit over-cautious overtaking a cyclist, and sod’s law dictates its often on a blind turn, or a blind hill, or a combination of the two, when I come up behind them. Its awkward for both of us, they probably feel a bit of impotus to crack on but are knackered, I’m trying to go up a hill in 1st at 5mph in a large estate without accidentally revving alot.
The friendly wave, thank you, hi etc can just relieve that and mean we both go about our day happily. Yes, Unklehomer tends to overthink things…