You can set Firefox to always show your windows and tabs from your previous session each time you start Firefox.

When Firefox starts, a single window is opened by default, displaying your specified home page. *unless you want to get into memory forensics and you're lucky and haven't overwritten it in memory with other data since. Session Restore is a useful feature in Firefox that remembers certain information about your previous browsing session so that you can continue work right where you left off the last time.The feature saves open windows and tabs, the size of each window and its position on the screen, as well as all. Restore the previous session every time you open Firefox. You should also note that this makes it possible for a local Mallory, with physical access to the device that Tor Browser is run on, to be able to reconstruct your browsing history. If you're not concerned about being anonymous and unlinkable, you can disable this through the Tor Button (Green Onion) -> Privacy and Security Settings and unticking Don't record browsing history or website data however you will not be able to restore the previous session. the tab is restored) the same value is once again in the website address, so Mallory can confidently link the two sessions (it's either you or someone you shared the link with) and use it as an opportunity to reinsert all the other tracking mechanisms that didn't persist. Your suggestion that 'there's really no difference between reopening tabs vs opening them for the first time' is false, in this scenario Mallory just puts a unique identifier value, specifically assigned to you, in the website address when you first visit.

If you're suggesting Tor Browser should write to disk, then you should understand that it is designed not to. There is no (reliable*) way to restore it once it has been closed. Since it doesn't store sessions, there is nothing to be recovered. In other words, it would make you trackable and remove much of the protection Tor Browser provides. When the session has been completed incorrectly, Firefox tries to automatically restore the previous session based on the data in this file with all windows and tabs that had been opened before the browser failed. It doesn't store 'sessions', this would constitute a persistence of state between uses, which would provide means for linkability between your various browsing sessions.

Firefox restore session on startup