Scenario

From Wildermyth Wiki

Scenarios are how Campaigns or standalone Missions are started from the main menu. Campaign scenarios are the main scenarios players will use, accessed from the New Game button. Mission scenarios are used to test out missions from the menu (via Tools > New Battle) without needing to start a full campaign, and are generally more for developer use, though players can also access them.

There's a "scenarios" section of the Content Editor you can use to create scenarios.