@droftarts Maybe I already do and maybe I am confusing myself. So I have..................

M584 X3.2:0.0:0.2 Y3.1:0.1:0.3 Z3.0 U0.0 V0.1 A0.2 B0.3 E1.0:1.1:1.2:2.0:2.1:2.2 P7

and

M669 K8 A0:0:0:0:0:1:1 B0:0:0:0:0:1:-1; CoreXYUV plus AB force cancelling gantry

Then this

M906 X1800 Y1800 U2300 V2300 A1800 B1800 Z1800 E600:600:600:600:600:600 I20

So in that scenario, taking just the X axis motors, I have 3.2:0.0:0.2. But 0.0 is also U and 0.2 is also A.

So what is the motor current for driver 0.0? Is it 1800 as per the X axis, or is it 2300 as per the U axis?

Edit. And after all the axes have been homed, the P7 parameter in M584 gets changed to P3. Does that then affect/change the motor currents?
Edit 2. Sending M584 P3 then sending M906 reports the same motor currents as having M584 P7 so I guess that answers that question. It's just what is the motor current when a motor is assigned to 2 axes that remains.