The easiest way to think about it is as two sets of automation tracks: the shared set and the personal set. With personal syncing off, the app loads the shared set and any additions go into the shared set. With personal syncing on, the app loads the personal set and any additions go into the personal set.
Between the set of automation tracks you already made for your singer, and the new set you want to make for yourself, could either be considered a "default" or shared set? Or would you consider them both personal sets that nobody but you two would ever use?
If you can consider the existing set as the shared set, then you just need to turn off personal syncing for your singer so he sees them, and turn on personal syncing for yourself so you can start creating your own personal set.
If you want the existing set to be a personal set for the singer, that will require some intervention from me. Please submit a help ticket to proceed with that:
https://helpdesk.arlomedia.com/arlomedia/add.htmlNote that with the first approach, anyone could edit the shared set of automation tracks in the future, but in the second approach, only your singer could.