You can manually set the stall current for a locomotive. Without the hand controller in front of me, I couldn't tell you how. But I have done it while experimenting with all the capabilities of the RailPro system.
Well I'll be danged. You made me curious so I had to go look. So in the habit of using Auto Set I have never done it any other way. Doubt I will have a need but nice to know the option is there.
To Dean's point, don't use the manual measurement Ohm's Law method to set the RP stall current. It won't be correct.