Shape Key Editor
The Shape Key Editor is used to adjust the animation timing of shape keys. These are stored inside an Action data-block. It lets you edit the value of shape keys over time.
This mode of the Dope Sheet uses a similar interface as the Action Editor Mode with the distinction of the absence of header filter controls and tools for channels.
In the Dope Sheet’s Mask Mode mask shape keyframes can be selected and edited. All Mask data-blocks in the blend-file are shown.