You define the morphs by drawing control lines on the objects in the Va and Vb tracks. Each line is visible at both Va and Vb windows:
You can drag the line or end points (of the currently selected line) in both windows separately. This way you can define how a line corresponds (for a example an eyebrow on a face) to the same line in Va/Vb. The longer the line, the bigger the impact of the morphing for this line. You can select the current line by clicking on it or by using the "Line:" numeric entry field. There can be up to 100 control lines.
To add another line, click the Add Line button. To remove a line, click the Rem. Line button
The "Line->" and "<-Line" buttons copy the line settings from the left window (Va) to the right or vice versa. So you can define for example the line for an eye-brow in the "Va" window, copy the settings to the "Vb" window and adjust the line in the "Vb" window to the eyebrow on the other face.
For a better understanding of the Morph transition, look at the demo supplied with MainActor Sequencer.