Understand the map hierarchy on your maps
The Map overview window provides you with an overview of the map hierarchy set up in the XProtect Smart Client. To open the Map overview window, right-click the map and select Map overview or select the icon 
on the map title bar.
A plus sign (+) next to a map indicates that the map could have one or more sub-maps attached to it as hot zones. Selecting a map in the Map overview immediately displays the selected map in the view.
Content in the Map overview may take some time to load if you’re connected to a very large XProtect VMS system with many maps.
If you’re connected to a XProtect VMS system that supports Milestone Federated Architecture, you can only add maps from the XProtect VMS system server you logged in to. Milestone Federated Architecture is a system setup with related but physically separate XProtect VMS systems. Such a setup can be relevant for, for example, chains of shops with many separate—but related—XProtect VMS systems.
See the XProtect Comparison Chart on https://www.milestonesys.com/products/software/xprotect-comparison/ for information about which XProtect VMS products support Milestone Federated Architecture.