If you have already created additional Trainers, but later wish to remove the trainer's account (perhaps they have left the business), then instead of completely removing their account you can instead set them to a 'Deactivated' state. 

In a deactivated state, the trainer is unable to login or use the system in any way, nor does their name appear in new client bookings etc. Their history will be kept and you can reactivate their account at any time.

Under the Trainer's profile, you'll see a 'Deactivate Trainer' button:

To reactivate, simply select the 'Reactivate' button:

Note: deactivated Trainers do not contribute towards any billing count (applicable on legacy plans)