Rated 5 out of 5 stars

I literally switched to Firefox Quantum today, because Vivaldi was simply too slow compared to Quantum.

This feature alone is the number one thing that kept me with Vivaldi. Can't wait for the port to Firefox 57+!

This review is for a previous version of the add-on (1.4.1). 

Thanks for the review! The beta version is now a WebExtension: https://addons.mozilla.org/en-US/firefox/addon/vivaldifox/versions/beta