If the Read&Write for Google Chrome toolbar is open in Google Docs or Slides a purple tab will appear at the top of the screen.
If the toolbar is extended it will appear as below
To close the toolbar, click the drop down menu at the far right of the toolbar.
Select Close Read&Write
Once closed the tab with the purple puzzle piece will no longer appear. To reopen the toolbar in Google Docs or Slides click the purple piece icon to the right of the Chrome Omnibox address bar
The Read&Write for Google Chrome toolbar will then open in Docs or Slides