Use model.component(<ctag>).mesh(<tag>).create(<ftag>,"Union") to unite meshed entities in 3D. Supported input: entire geometry, unmeshed domains, boundaries adjacent to unmeshed domains, isolated boundaries, isolated edges, and isolated points.
Use DeleteEntities to delete domain elements while keeping the unmeshed domains. If a subset of the faces are selected for the operation, it might not be possible to update any existing domain information. Use
CreateDomains to recreate the domains, if needed.