TR is based on a single-user account use, so there is no easy way to pick through workouts done by different people. There is no built-in way for them to filter workouts by user, since that use is not supported.
At best, I could see using the Search function on the Past Rides page to search for the different rides. But that relies on having unique data in one of the searchable fields (like the workout name or ride notes).
Then you have to delete each one manually, that you don’t want retained.