I'm very, very glad that you decided to update/revive this add-on and allow it to transition into the WebExtensions world. Like many people who use it, I quickly found it to be one of my most useful extensions that I really don't want to browse the web without anymore.
I'm quite sad at the usability issues that are forced by Firefox, because they make using the add-on a lot more cumbersome than it used to be. From the looks of it, not allowing an extension to add multiple top-level context menu entries is one of the major gripes people have, and I totally understand. Your workaround is a decent temporary fix, but I really hope Firefox developers will lift this restriction very, very soon. It's just not acceptable to put that kind of restriction. Also, it's completely ridiculous that they don't allow customisation of shortcuts, because that actually *increases* incompatibilities between extensions, rather than reducing it.
I'm still giving you the full five stars, since there's no point in criticising you for issues that are 100% down to the short-sightedness and incompetent decisions on Mozilla's side. I hope the users of your extension, and others suffering from the same inane limitations, will build enough momentum to beat Mozilla into coming to their senses.