To clear a tablet menu assignment
- Click Tools
tab
Customization
panel User
Interface. 
At the command prompt,
enter cui. - In the Customize User Interface Editor, Customize tab, in the Customizations In <file name> pane, click the plus sign (+) next to Legacy to expand the list.
- Click the plus sign (+) next to Tablet Menus to expand the list.
- Click the plus sign (+) next to a tablet menu to expand the list.
- Right-click the row or column that you want to clear. Click Clear Assignment.
- Click OK.