2022-01-12 12:09 UTC+01:00, Patrick O'Callaghan <pocallaghan(a)gmail.com>:
You might consider the Tab Session Manager extension. It
periodically
(or on demand) saves your current tabs and windows and can restore them
again on startup, but optionally not actually load each page until you
decide to visit it.
I believe that this is the default behaviour of Firefox. I mean the
"not actually loading until you switch to it" part. The restore part
is not the default, just an option. But neither needs an extension.