It took me years… YEARS to figure out a reliable way to trigger the #GNOMEWeb / #WebKitGTK bug where the native general "Copy/Back/Forward/Reload" right-click menu would show up on top of GMail's custom contextual menus.
Finally I found a 100% surefire way to make it happen. Now it seems so straightforward, all of a sudden
https://bugs.webkit.org/show_bug.cgi?id=258746#c5