The Mouse buttons are fully customizable. The Mouse Click category enables you to define keyboard shortcut keys for the following mouse commands:
Pick (Left button) – Geometry pick and not menu
Exit (Middle button)
Sub-Menu (Right button)
Reject (Left & Middle buttons)
Pop-up menu (Right & Middle buttons)
Filter (Right & Left buttons)
The mouse is also used in combination with other keys to Zoom, Pan and Rotate entities.
When you enter this tool the Customize Keyboard dialog is displayed. Scroll the Categories and select Mouse Click.
See Customizing Hardware for a description of this dialog and also for details on how to create and edit shortcuts.