Tab Stash doesn't save blank tabs by design, though you can explicitly save them using drag-and-drop, selection, etc in the UI. The reason being, most of the time, these tabs are just clutter.

And yeah, I hear you on operations involving lots of tabs being slow—unfortunately, most of this is due to Firefox. I do try to keep Tab Stash's performance as high as it can be, but there's only so much I can do if Firefox itself is slow.

Also hear you on the language support. It's a really big effort to even get Tab Stash ready for translation into other languages, and it's been on the list for a while now. I do hope to get to it one day (and patches from others are always welcome).

Thanks for the feedback!