Your first request is something I know as I also need to duplicate tabs. :)
I'll work on something after the whitelist feature.

About the "Priority", "Filter", etc I've tried to explain this in the description of the add-on.
Filters allows to define how you want to compare the tabs.
Priority allows to define which tabs to not close.

I'll move the code on GitHub, just to have time.

Thanks for the review.