Indeed this is not something supported by Klipper out of the box. Besides the PR you referenced, you may find it useful to try the new generic_cartesian kinematics being developed. There I added a support of the SET_STEPPER_KINEMATICS command. While originally I had other usecases for it in mind, you could conceivably use it to scale the stepper movements for a given axis in case you have a plain Cartesian kinematics, e.g. if you have in the config
[stepper x]
kinematics: x
....
then during the print you could issue commands like
SET_STEPPER_KINEMATICS STEPPER='stepper x' KINEMATICS=1.005x
which would make stepper move 0.5% more on X axis movements.
Just one thing to keep in mind, regardless of which approach you choose. It is very important where the toolhead is when you change the rotation distance or axis scaling. This is because when you change the scaling, the toolhead won’t move, but all subsequent moves will be scaled relative to the position where the command was issued. So you may need it to be either in the center of the print, or stable on one side of the print, depending on what you want to achieve exactly. Also, I don’t think axis scaling would work well if you are printing in vase mode, as you want to scale the axis with Z, and in vase mode Z changes continuously.