As far as I've been able to figure it out, you need to draw your frames in the frame editor, select the frames you wish to morph with the shift or ctrl key, drag and drop them into the scene you wish to put them (they will be pasted as a single scene), select the morph option and hit the play button.
The morph start to end frame option will morph the starting frame to the end frame, regardless of how many different frames you have in between.
The morph all frames option will morph all frames in steps, that is, it will morph frame 1 into frame 2, then frame 2 into frame 3, and so on.
So far, that's all I've got. Let's put our collective heads into this and see if there are more options, shall we?
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