Version 1.6 now includes CTRL+SHIFT+D and ALT+SHIFT+D to duplicate the current tab. I wanted to make this configurable but I couldn't find a way to with the current WebExtension api. If I find out that I can in the future I will make it be configured.

It would be easier for me to help if you put feature requests and bugs on the repository issues https://github.com/Skeletonxf/duplicate-tab as I'm not getting notifications when you edit your comment (and I doubt you get them for me).