Say I define different contexts or workspaces. So in my address bar I can type work and it will open up 5 pages that will be associated to that keyword. Then I can type bored and it will open up my 4 defined pages associated to that keyword.
I am NOT asking about pinning pages to the start/home page, and I am NOT asking about loading websites when Firefox starts up (because I don’t want to always load the same things every time I launch ffox). I am also not asking about pinning tabs.
You can also middle-click the bookmark folder itself.
Or you can open a second window, open all your work sites, then pin the tabs. If you have at least one pinned tab in the first window as well, even if that pinned tab is just about:blank, both windows will re-open when reopening firefox.