With Firefox, Chrome, and Chromium, I can click anywhere in the tab bar that doesn't have anything else in it to grab and drag the browser window. Unfortunately, with #Vivaldi (on GNOME on Linux, at least), you can't click and drag the window between the "+" button for creating new tabs and the window control buttons on the right. This is an annoying bug that will force me to retrain my muscle memory for no good reason.