Was a 5 (will have to drop soon). With the 3.0.0 upgrade on 2018March20, on Firefox 58.0.? and then soon after on Firefox 59.0.1 (64-bit version) on Windows 7 Professional, the clicking on the Add-on icon in the toolbar, the saved session navigation tool would display but would be blank (I have a lot of saved session, so I pretty miffed for a little bit). I tried to save some new ones, to no avail.

That said! After futzing around with pretty printing the storage.js file appears to be intact, and the Add-on appears to be auto-saving the various tabs on the defined interval (15 minutes, I think).

I'd love to see a fix appear, because I really don't want to have to write a perl script to extract all of those backslash escaped URLs in the file (or do it by hand! :-O )

Thanks for a (usually) great tool.