You could create a config file for your GameMode or GameInstance using whatever your preferred data format is, store the data for the values you want to override inside the config file, and then load the config file into the GameMode or GameInstance from a GameMode Blueprint or GameInstance Blueprint with a script. The EUW would then need to be designed to edit the config file instead of interfacing directly with the GameMode/GameInstance. From there, you could do other things like making a custom event to scan the config file for changes if you wanted to do something like that during play as well, but that would require an in-game configurator in a UMG menu rather than just a EUW as well. That’s also beyond the scope of what you asked, I guess, so I’ll stop overthinking things now.