Yes this UI is new, there was an unofficial add-on [0] before that did something similar.
During my internship this summer we also added Push capabilities to decrease the time it takes to send a tab to another device (it used to be in the order of minutes).
During my internship this summer we also added Push capabilities to decrease the time it takes to send a tab to another device (it used to be in the order of minutes).
[0] https://addons.mozilla.org/En-us/firefox/addon/send-tab-to-d...