Just close them. You're never going to read them. If you really think there's something you need, export the browser state to an archive file, then delete in 10 years after you've never consulted it once.

(Disclaimer: I'm aware that there may be valid reasons for this workflow, but in most cases it's just digital hoarding and the above advice is sorely needed. If you really need 1800 tabs, you know who you are and you can safely ignore me.)

Brave has a function to bookmark all open tabs. I have used that from time to time. Or just made a temp file and written all the URLs to it, in case I want to open a few/dozen of them after rebooting.