To select maps in Multimap Workspace:
To select a single map click on it.
To select multiple maps, hold the Ctrl key and click.
To select all the maps click the Select All button or press Ctrl+A.
You can also use the arrow keys to move between and select maps.
Note that you can choose the number of levels of linked maps to display. The maps are displayed only as previews, but you can double-click to open any map individually in Map View. The map's "level' in relation to the parent is displayed as a small number in the lower-left of the map thumbnail image.
You can also choose to display small, medium or large thumbnails.
Once you have selected one or more maps from the workspace you can use the Multimap commands.