A digital video builder system with methodology for designer-controlled user interaction is described. In one embodiment, for example, a method comprises receiving, from interactive controls on a graphical user interface, configuration of a storyboard block of a storyboard of a target digital video to be created. The storyboard block represents a scene of the target digital video, comprises a media element slot and a scene parameter for configuring the media element slot, and corresponds to a scene specification having a plurality of scene variants for rendering the scene of the target digital video. The received configuration comprises a setting for the scene parameter. Based on the scene parameter setting, the method further includes automatically selecting one of the plurality of scene variants for use in rendering as part of the scene of the target digital video.