All you have to do is to connect the new device (laptop) to the same Firefox Account (email and password).

• https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer

Unfortunately that doesn't work for open tabs. (I already I found an alternative workaround for bookmarks and passwords so am not sure whether it worked for those.) Also, I don't have the 'three dots' option (page action menu?) next to the URL to facilitate sending tabs to another linked laptop.

You can find "Send Tab to Device" in the right-click context menu of a tab because the three-dot page actions menu is no longer supported.

You can copy certain files with Firefox closed to the current profile folder to transfer or recover personal data. Note that best is to avoid copying a full profile folder.

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

• bookmarks and history: places.sqlite
• favicons: favicons.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (encrypted logins;32+) and key4.db (decryption key;58+) for Passwords saved in the Password Manager
  key3.db support ended in 73+; to use key3.db in 58-72, make sure to remove key4.db
• cert9.db (58+) for (intermediate) certificates stored in the Certificate Manager
• persdict.dat for words added to the spell checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)