Automatic in-between frames

On a layer, draw the two keys of the motion: the start and the end. F6 creates a key that copies the drawing; F7 creates an empty key.

In the timeline, select the range from the first key to the second, at least three frames long.

Use Animation → Tween motion to move, rotate and resize the objects between the keys, or Animation → Tween shapes to turn one outline into the other.

Check it with Animation → Play / pause. The whole tween is a single edit in the history, and Ctrl+Z undoes it.

Tween shapes needs compatible vector outlines, without crossings and without holes that change. If Zyggs warns that the transformation would collapse an outline, add an in-between drawn by hand or simplify the stroke.