You can export your dashboard, queries, alerts, agentsgroups and extracted fileds as a content pack. Navigate to content pack menu in the left menupane select My Content or Shared Content. Then in the main window beside the name klick the gearicon and choose export.
here is a link to the official instructions from VMware
this approach applies to all shared dashboards, but not the user specific ones (export of "my dashboard" for every user).
No I couldn't find anything that could extract other users dashboards. There probably isn't an official way as the Users has choosen not to share it so it's "private" to that user. So if there is a way my google-skills can't find anything i'm afraid.