Reusable mappings are more general objects than standard mappings and can be shared not in context of particular question. For this reason the window allowing to manage access to them can be entered via from search bar.
After clicking the button Manage access, you will see the similar window as for managing access of recodes and user-defined questions. Again, it is possible to give user/folder a Full or Read-only permission. You should proceed in the same way as described in the chapter Access to user-defined questions and mappings.