Some extensions does allow to import/export their preferences/settings which is useful when installing those for a new profile (same as the case when installing Firefox freshly after reinstalling windows) and while syncing multiple Firefox installations. Manually you don’t need to export or import Firefox extension preferences because there is an extension for that, OPIE (ordered preference Import/Export).
After installing this add-on, you can observe its icon on Tools menu (press Alt+F), you can also drag and drop OPIE icon from customize Toolbar window by Firefox menu>Options>Toolbar layout.
Now to Export extension preferences click Export tab and browse for export directory create separate one if not exists. Click “Get list” button and select all or choose desired ones and click Export button, a message pops up when new export files for extensions are created.
This extension by default during the export, creates individual preference files, however you can export all of them to a single named file, this option available on the Export tab.
To import Extension preferences click on “Import” tab Browse for files to import, select preferences and click Open button followed by clicking the Import button.