If you want to hide the Chrome extension temporarily, you can click this button:
And to show again, you can click this button:
However, if you click this button, it will hide the Chrome extension permanently for this email address
If you did this inadvertently, you can undo by first going to Gmail and then opening up the Chrome Developer Tools panel.
Then navigate to Application, open the Local Storage dropdown, and click on https://mail.google.com and you will see the propellerCRM key
Right mouse click on the propellerCRM key and click Delete
Now close the Developer Tools panel and refresh your browser.
You should be back in business.