For what it's worth.... If you're going to delete all your engines so to speak and start over , Reset the remote(s) as a first step,,, This will delete everything and give you a clean slate to start over and edit the engine's addresses to whatever you want.
Adding engines... Find a good spot with a perfect dcs signal. add an engine here with no other engines receiving power anywhere on the layout.
Once the engines has added, shut down layout power for 30 seconds or so, power the layout back up and see if the engine will start up. It should .
Having said that, if you decide you want to edit the engine's address, Go ahead with the EDIT address command under the engine set up menu,,,,, The test now is the will the engine remember the new address?
So back to power down layout again for 30 seconds. This time the engine should start up with the new edited address. If successful , now would be a good time to add the engine to the second remote, (Yes I can hear RJR in the background) It should add to the new edited address as well. Each remote must have the same ID for the engine.
You're going to have to do this with each engine that you have to add.
Engine's ID stick with the engine unless factory reset ,edited or ID is taken by another engine when trying to add, In this case the engine adds to the lowest available ID.
We have 8 remotes and line them up near the programming track and start adding making sure the engine added has the same ID in each remote... It goes by quickly. (I can still hear RJR screaming at me)