Good evening, @suzi102. 

Thanks for chiming in on this thread. 

The merging of employees is only possible if the employee you intend to merge doesn't have existing payroll transactions associated with their profile. This guarantees a seamless process without any conflicting or duplicated payroll data.

Review this guide for more details about merging lists in QBDT. 

I hope this helps answer your question. I'm only a post away if you need me again. Take care!