I think what @LouP is saying is that if you have an activity already setup on the remote with, let's say, a TV, and an A/V receiver, for example, but then later you realize you want to add another device to that same activity, like an Xbox or streaming stick or something, the only way to add another device is to go back into the wizard, but then once you've selected the new device and continued through the steps of the wizard, any custom button mappings you had set up (like assigning rare misc functions to number keys or something like that) get reset to their default mappings. I have experienced this several times as well while fiddling and tweaking my setup.