Then there's a second option called dom.event.contextmenu.shift_suppresses_event which defaults to true and does what you said: Simple right click opens the page menu and shift + right click don't send the page the event at all and instead opens the browser's menu.
https://webextension.org/listing/allow-right-click.html https://addons.mozilla.org/en-US/firefox/addon/re-enable-rig...
I wish there was a setting for "right click works, hold shift key for wanky behavior"
When I run into a site that doesn't want to let me select/copy text, I screen shot the page -- in Photos on iOS, and in Preview on MacOS, selecting text out of an image generally works great. Just tap and hold a moment on iOS, or hover a moment on MacOS, and then drag/click-drag to select.
Left button rotate, Right button pan
Left button gun, Right button grenade.
document.designMode = 'on'