Pitter wrote on Mar 14^th, 2020 at 6:12pm:

I load for example the FDX with 80to and fly from KJFK to KORD. When finished after ldg I save that flight.

Right, the 777 FDX with 80to at KORD is saved in that flight.
If you wish to change airline or airport but keep the payload:
1. Select that saved flight.
2. Select airline or airport.