Is this about setting the home page to multiple pages (i.e. currently opened tabs)?

You can do this via "Options/Preferences -> Home" (about:preferences#home).

• https://support.mozilla.org/en-US/kb/how-to-set-the-home-page

There are people here, Frick.

Here's how you get to it:

(1) Open the Options/Preferences page:

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Any system: type or paste about:preferences into the address bar and press Enter/Return to load it

(2) In the left column, click Home

Then on the right side:

(3) Change "Homepage and new windows" to Custom URLs

(4) Now click the Use Current Pages button to fill the addresses of the current set of tabs

Success?