This information should be stored in the <code>browser.uiCustomization.state</code> preference, so you should be able to just add that preference to the list of things that Firefox has to sync. To do this, go to the <code>about:config</code> page in Firefox and bypass the warning (if you see one). Then type <code>services.sync.prefs.sync.browser.uiCustomization.state</code> into the search bar on that page. Since that preference doesn't already exist, you will have the option to create a new preference. Make sure that it's set to <code>Boolean</code> and then press the <code>+</code> button. Make sure that when it's created, it's set to <code>true</code>. Before you sync other devices, you may want to trigger a manual sync to make sure that this new preference is saved to Firefox Sync. To do this, go to the Firefox options page in the '''Sync''' section and press the '''Sync Now''' button. After you've done that, add the same preference I referenced above to any device(s) that you want to share the same toolbar layout. <blockquote>'''NOTE:''' Because this preference is not standard to include in Firefox Sync, it may not sync correctly to all devices.</blockquote> Hope this helps.