Mouse gestures are in my muscle memory. I can't live without them, and every single Webextensions Chrome mouse gestures addon either:
a) Sucks. Doesn't work at all on internal pages including new pages (which is not a blocker, but sucks), and more importantly doesn't work _well_ ANYWHERE. Inconsistent behavior, poor performance. Just unacceptable.
b) Is actually literally malware. Once Chrome extensions get popular, a shady Chinese or Russian consortium buys them up, adds user tracking, and silently updates the extension so your every move is followed.
Chrome has been around for almost 10 years now, so I'm absolutely convinced that Webextensions are unable to support _GOOD_ mouse gestures.
Now that Firefox will shortly become hot stinking Chinatown garbage, my only hope will be Vivaldi, a browser using Blink (Chrome's backend). Its mouse gestures are really close to being usable-- it only lacks configurable mouse button chording.