Nice, useful addon, though it's too bad the newer versions can't be used on <Firefox 57. Also, an option to open the menu on left-click would be nice, and it definitely needs the ability to export/import the settings, which is the main reason it's not 5-stars.
Edit: Down from 4 to 3 stars since not only am I forced to use an older version, since the newer versions aren't compatible with <v57 (running Waterfox), but I keep telling it not to show me the warning message about the flags getting out of date yet it KEEPS showing me the message anyways. If you're going to update it in a way that leaves a large portion of your users behind, at least don't rub it in our faces.
Second edit: Back to 4-stars now that I'm using a more up-to-date version, though it would be nice if it could be added to AMO or at least be signed by Mozilla. And I still would really like to see the ability to backup the configuration. As previously mentioned, that would make it near-perfect.