Then we split that group into 2 separate groups ex. Windows Admin B and Windows Admin C. 

We did not delete the old group since we still had multiple tickets assigned to the original group. 

We are now back to one group again, is there a way to reassign all the tickets from B/C and move them back to A that would not involve manually looking for each ticket and re-assigning it?

We will eventually delete Windows Admin B/C.