Yes there is. In the Campaign Editor, you have to be in the part of the menu where you are attaching the maps to your campaign (on the right you have to see all maps of your campaign one over the other.)
If you are in that place, scroll over the few options at the top of the Campaign Editor and one of them has Gameplay Constants in it. These Gameplay Constants will be used by all maps in your campaign. I think most if not all Gameplay Constants options from a singular map take precedence over the Constants from the Campaign, but only if a Constant is changed.