How can I copy/re-use a map?

We presently don't have a "reset page" type of feature, but what you can do is create a master copy of your board as its own campaign. Set up your master and whenever you want to run the game, copy/extend the campaign to make a duplicate and play your game with the duplicate. That way the preset master is always available to be copied for a new game. You can access the Copy/Extend feature when you click on a campaign in your list to bring up its details page.