How I can give a soft limit to the for the specific axis using bg logic
Is this to stop the robot if in forbidden area?
If yes, this can be even done in BG logic, but the reaction time may appear insufficient for fast moves.
Or, probably, may be done by Inteference Check, with fixture models modified programatically on demand.
If, however, the axis limits are intended for MROT motion, they must be system settings and yes, require power cycle after modification.