To select multiple items in the 
Guests, 
Groups or 
Schematic pane:
| • | To select multiple individual items  +click on each item. |
| • | To select a group of items click on the first item and Shift+click on the last item. |
| • | To select multiple groups of items +click on the first item in each group and Shift++click |
To select multiple items in the 
Floor Plan pane:
| • | +click on each item. |
To select all visible items in any of the above panes use Edit>Select All or +A.