The FlipBook tool and the ability to display multiple keyframes is only available in SketchBook Pro Desktop.
Use the Ghosting tools to see multiple keyframes. See the next frames and/or previous ones.The Ghosting tools (number 4) are part of the FlipBook Timeline.

Once you've created a FlipBook, use the Ghosting tools
to see multiple keyframes to get a sense of where to sketch next and what needs to be changed.

To see the previous frame, click
.
To see multiple frames, click the menu next to
and set the number of previous frames you would like to see ghosted.

To see the next frame, click
.
To see multiple frames, click the menu next to
and set the number of frames, after the current frame, you would like to see ghosted.
