You can try to sync the browser.uiCustomization.state pref by creating the corresponding services.sync.prefs.sync. pref and set its value to true.

• about:config page: services.sync.prefs.sync.browser.uiCustomization.state = true

I just tried what you suggested, but it doesn't seem to work. After adding services.sync.prefs.sync.browser.uiCustomization.state = true that entry gets synced with my other firefox and the browser.uiCustomization.state itself gets synced aswell. But there are no changes on the toolbars. Manually changing the value of browser.uiCustomization.state also does nothing. After a restart the manual changes are lost. Also changing the value in prefs.js, when firefox is not running doesn't change anything.

I also tried swapping some entries in localstore.rdf in the nav-bar entry, but those changes aren't affecting anything either.

Does this have something to do with it maybe?

These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose.

OPIE {web link} Import/Export extension preferences

Thanks for those add-on suggestions, but I can't find any option that includes the toolbar settings. And since I don't know from which files these settings are read, I can't use the user-defined backup to sync a specific file.

Does someone know the right files to sync?

localstore.rdf Holds most user settings including toolbars and placement

Open the FEBE options menu thru the Add-on Manager or its own icon (by pressing its arrow).

At the top: Select What To Back Up. Backup Type: What user data do you want to save. User-Defined: What other files do you want to save. Ignore List: What files not to back up. Note: Some items can’t be backed up by FEBE.

Select User-Defined. Edit: Change settings for a currently saved item(s) Delete: Remove a saved item. New: Add a file or folder to be saved during a backup.

Press the New button. Select Type: File or Folder. Enter something in the Label and Description (Required) On the right, press the Browse button. Find the file or folder you want and click it once. Press Open. Check the box labeled Include In Backup. Then Submit. When you are done here, press Post Entries and Save.

Select Where to Backup Choose where you want to put the FEBE backups (outside Firefox). Example: C:\Users\=<username>=\FireFox Backup Select the type of time stamp for the folder name during backup. Maximum Backup Directories: I use 30 – 40. Just In Case.

Select When to Backup. Decide when FEBE creates automatic backups. Mine is daily AM. You can also have FEBE do a manually backup at any time.

How To Backup: Options Advanced: More Options and Tools.

I already played around quite a bit with localstore.rdf. As I wrote before, none of my manual changes in that file are changing anything in the toolbars. Even replacing the whole file with one from another computer does not change the toolbar settings, while it seemed to change some other things like making the window fullscreen. This happens even with a freshly created profile.

Could someone try if their manual changes in localstore.rdf are affecting the toolbar settings?