Which function and access privileges do you need for a merge?

Function privileges

Access privileges (source database)

You need Read access privileges for all groups you want to transfer items from. The models and object definitions you use do not have to be in the same group. In order to transfer a model completely, you must also have the Read access privilege for the groups containing the object definitions.

Access privileges (target database)

You need the Write access privilege for all groups in which you want to create items or change existing ones.