It is possible but not really straightforward.

Look at the Probe setting in the Channel menu. Note the large variety (16) of multiplication choices there. And in the Unit setting, you can choose "A" for amps.

So you have to do a little math outside the scope. In the simplest case, say you are using a 1 ohm shunt and monitoring the voltage across this shunt with a direct connection, no probe (or 1x probe). So you choose "1x" for the "Probe" and "[A]" for the Unit. Then your channel display will be correct in Units and numerically, and display reading in Amps, and you can then use the scope's Math for, say, CH1 (amps) x CH2 (volts) and get a result correctly displayed in watts on the Math channel.

So you have to choose your shunt resistance and Channel probe attenuation values so that you can set the "Probe" value from the 16 choices available in the Probe menu to have the correct numerical current value displayed on the channel.

Yes, it's a pain all right, but it can be done. Another even more "kludgy" way of doing it is to provide a constant voltage on one channel and then use that as the "constant" for a Math operation like CHA/constant.

Why Digol....er, Rigol didn't simply provide the ability to enter and use a constant in the Math operations is beyond my ability to explain, except to fall back on the old "it's only 400 dollars, what did you expect".

By the way your "poll" doesn't make sense to me.