Indeed. It's going to be opt-in somehow, probably based on the character sheet supporting it? But at any rate, the idea is that for example if I'm using the 5E OGL sheet, as a player if I change the "Class" element, some of my attributes get automatically set up for me. Right now if the API were to make that same change (setting "Class" to something), class would change but the sheetworker code wouldn't run. So your only option currently would be to duplicate all of the code on in the API script that's also in the sheetworker, if you wanted to maintain that automatic logic. The new feature would basically allow the API script to "dumbly" just "set class", but then there would be another piece of the API that would come along afterward and go "oh, I notice you just updated Class! Well I have some sheetworker code over here that needs to happen when that happens, so I'll run it!" It basically allows the API to do anything a player can do in terms of a sheet and still have automated sheetworker logic happen.