If OpenList [1] on Chrome was ported to Firefox (ahem, someone please do this), you could do this trick: * Use openlist to copy the list of URLs that you currently have open. * Paste the list into something. I use sublime because it will remember your _unsaved_ tabs. * Paste back into a new window later with OpenList to open them all.

[1] https://chrome.google.com/webstore/detail/openlist/nkpjembld...

This extension is also really helpful for mass URL-manipulation when you're too lazy to write a full script, but want to mash on some API. Someone please make a 1:1 port :D