This is an example widget to show how the Secondary sidebar looks by default. You can add custom widgets from the widgets screen in the admin. If custom widgets are added then this will be replaced by those widgets
The Track Matte Key effect reveals a background clip through another clip, using a third grayscale image as a matte that creates transparent and opaque areas for a superimposed clip. Using the Track Matte Key effect requires two clips and a matte, each placed on its own track in the Timeline.