To my knowledge there is no requirement to schedule the effects of humidity in helicopter flight manuals, so it isn't done.
In days of yore when helicopter performance was sometimes very marginal, it was done. I am thinking of the Naval Westland piston engined Whirlwind HAR Mk4.The pilots' notes had a graph giving the correction of MAUW for 180 ft/min performance.
In the RAF SAR Whirlwinds, the navigator consulted the WET/DRY bulb figures every morning and computed the max weight for the day. From memory, between totally dry air and 100% humidity, the difference was about 5%.
Rather an important consideration in the Far East theatre.