What happens if you choose:

History > Restore Previous Session

Another possibility is to use:

• Firefox > Preferences > General > Startup: "When Firefox Starts": "Show my windows and tabs from last time"

That works but only for 1 level down. How can I do another day or time?

I didn't see that under that section or anywhere in prefs.

That works but only for 1 level down. How can I do another day or time?

I don't think session restore can capture more than one point in time (the end of your previous session). There could be add-ons that extend the session restore feature (I haven't searched).

If you want to save your open tabs to re-open at any time, try Bookmarks > Bookmark All Tabs to create a new folder of bookmarks for the current window. Note that these will be opened fresh, so will not resume the session as of the time you saved them (you might have to log in again), and you need to do it for each window.

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To see more history, try History > Show All History.