You will find this button on My Account page. When you click this button, you will be signed out of all session wherever you logged into superblog dashboard.
For example, assume that you logged into a superblog dashboard from a public machine. But you forgot to logout! No worries, you can login to superblog dashboard from any machine and then visit “My Account page” to click “Logout All Sessions” button. Now, your active session from the earlier public machine is also logged out!