I think ultimately, the issue is do you give the supply a SIMS login? If the supply member of staff has got access to SIMS, the cover manager can assign the supply staff with the relevant classes. This way, the registers appear on the SIMS homepage for the supply staff. If you don't do cover through SIMS, you can still pick up other teachers groups through the take register icon. You don't need to have a member of staff registered through the timetabling software to take their class register.