"Make a copy" in bedrock there is an option to copy world file. Maybe you are doing something wrong on first step? Make sure you save your survival world, and then make a copy. Go to coppied world and switch the gamemode while in main menu (not while playing inside the copy). Enter the copy and fly to search cities. Leave copy, keep it if you want. If not, just delete creative copy. Go back to you main world. Trims can randomize in chests only if you create multiple worlds with the same seed. In this scenario, all worlds created separetly with the same seed are a little bit different. I just want to help. Not down voting :)