David Gurk

Each window creates an own independent PTG stack.

> Additional to "Access your data for all websites" there is strange for me permission "Download files and read and modify the browser's download history" permission in this extension. It...

Sorry, this might happen in rare cases. Currently it's hard to tell exactly what could cause this. Try to download the backup within the addons settings and look in the...

@KenBallou You could check if the tabs are still hidden:  And you could look into the history for closed tabs. 

This is true. In this moment you could try the autoplacement within the freeform view or give the popup view a try. :)

I have no idea what could cause this. If it's okay for you to loose your browser session and settings, you could refresh your installation to start new. https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings

I think the number should not be visible. I could imaging to remove it from the view and only show it within a tooltip or so.

My wish for such kind of problem would be an automatic backup.

This might only work if it wasn't the last window.

Keep calm and try https://addons.mozilla.org/en-US/firefox/addon/tab-session-manager/