if you're flying for the airline I think you are then I know what you're getting at ! On the EFB enter the actual airfield, runway and ambient conditions and then the estimated takeoff weight from the OFP. To view the absolute max RTOW change engine rating from optimum to 26k, bleeds off, improved climb, then calculate. It will display the max RTOW for you now, enter the lower of this value and the max structural takeoff weight on the handling agents data sheet.
Hopefully a future software update will allow a max RTOW calculation without entering a guestimated takeoff weight
Regards.