Thank you muchly for the detailed feedback! I've made a note to add an "open in same tab" option, and was already planning to address your other points in the next version. Thanks for your patience!

Update: Version 2.1 is out, and adds your requested "open in same tab" option and a cache that tracks folders but not bookmarks for 15 minutes. The context menu, and a better, longer-lived cache, will come in version 3.0. I hope you enjoy the extension!