Is this hoarding? You should try to break this cycle. There's no way every single one of those hundreds of tabs is important to you. Take an hour or two to go through the tabs and manually create the bookmarks on desktop for only the ones that are most important to you. Let all the other ones go.

Genuinely interested why anyone would want to do this?

Hey! I do this too. It's a not so great habit but the Treestyle tabs firefox extension does exactly what you need. You can select all tabs and click bookmark tabs. I actually recommend another similar extension called Sidebery*. It can even create occasional snapshots so in the case of a browser or system crash you have backups on disk or memory.

EDIT: Oops, meant to say Sidebery not Tabby. Sorry, wrote that just before bed. Tabby is a great terminal emulator though!

Doesn't the sync work?
I can always jump into that section in browser and there are all the tabs I have across devices.

One possible solution is that all of these tabs will go into your history, which also can sync between devices if you configure it to. Once you have Firefox open on your desktop, you can click the hamburger menu in the top-right, history, manage history. Once in there, you can select all of the items in your history at once with ctrl-a, right click, then bookmark them all at once.

If it's crashing while trying to open the synced tabs, you may need to turn off the tab syncing first in sync settings.

@worldofgeese Hi. What I can think of is the following: use the TabStach extension (Firefox). Store there the tabs you want to keep there (those websites that you have marked for Research or reference but are not as essential as having them saved as bookmarks). TabStach works precisely the tabs as normal bookmarks (they even synchronize with the rest of the Firefox bookmarks). Finally, you export Firefox bookmarks (in the traditional way), either in HTML or json. TabStach has its own category.

Lol