I can’t speak to Garmin Connect but can help with the TR end. When you’re done with your ride & it uploads to TR, you have the option to edit it. Click edit & you will have the option to change your ftp for that particular ride which will bring IF, TSS & time in zone to appropriate numbers for that ride.
I think outdoor workouts are another story. I haven’t done any yet but I think I’ll have to manually change my ftp before the rides push to my Wahoo bolt to get the proper power target levels for my outside ftp. When I’m done, I think I’ll have to again manually change the ftp if I’m going to do a workout inside on the trainer.