How do we get this menu item on the toolbar.

And I want it Here:

Right click on the toolbar and click 'customize'. The customize window will open. Click on the 'Commands' tab and select the Toolbar 'Standard'.

Right now you click on 'Add command' and the following window will open.

Click on 'Edit' in the left pane, and Find 'Outline Collapse To Definitions' in the right pane.

Then hit 'Ok'

Move the command to the correct position and hit 'Close' and you're done.