Format -> Align -> Horizontally Distribute Space

→ Format Horizontally Distribute Space

This menu command is used for setting the horizontal space between objects you select. After you select this menu command, the following dialog appears:

You can choose the distance from 10 to 3000, with an increase of 5. You can also select the "Use as Default" check box to set the default distance.

The standard toolbar also contains an icon for this menu command.