An option in the Solid Mesh - Manual PropertyManager maintains the previously defined domain definitions when you create a solid mesh with the Manual method.
In the Solid Mesh - Manual PropertyManager, select Use Previous Design.
The program maintains the previous definitions for Cooling Channels, Runners, and Virtual Molds, and proceeds to the step of surface mesh creation. This option saves you time as you can modify the mesh for the cavity only, without redefining the domain assignments in a model.