A Roll can contain several master clips. Subclips can be created from these master clips. As a result, a Roll can contain a collection of various clips and their segments. The Subclip mode of the Roll window allows to effectively work with such clips collections.
When Subclip mode is disabled, all master clips and their subclips are displayed on the top panel of the Roll window:
The master clips are highlighted with blue frame. The currently selected clip is marked with the red frame.
Click the "Subclip mode" icon on the Roll window toolbar to enable this mode. The additional panel will be displayed on the left containing only master clips inside this Roll. Select the master clip and only subclips originating from this master clip will be displayed in the storyboard view.
The number on the top right corner of master clip thumbnail indicates the number of subclips originating from it plus the master clip itself.