I was running into an issue where there was 2 instances of NavXp added to a skin page, where one was providing horizontal navigation on large screen then vertical on small screen. The current manage button will only select the 1st instance to edit.  I then have a different instance for a second skin page.  I have a backend where I manage sections of the site (where the module listing page exists) and was after a way to manage the different NavXp instances.  You may need to be logged in as admin for the edit button to work correctly, runs on my site without issue