If you highlight something and right click it, you'll notice the "Search Google for (...)" option. I'd rather press something like "Alt + G" instead right clicking, aiming, and then left clicking.
Where to edit the hotkey - about:addons (in the URL), and then: - Manage Extension Shortcuts (the gear at the top right).
(Bonus): I'd recommend using AutoHotkey v2 to either 1) get around Mozilla's shortcut restrictions or 2) override the default ones. Reach out to me if you need help with that.
