RedRogueXIII has some Metasequoia Scripts on GitHub that can be studied to see how to create dialogs for your Metasequoia scripts.
https://github.com/RedRogueXIII/MetasequoiaScripts
The script shrinkwrap.py didn't work for me because for some reason the target object was not being set. I had to hardcode the target object. Since I had only one object in the target list I had to make sure I clicked on it for it to be set.
The script moves the selected vertices in a source object to the surface of the target object if a ray from the vertices in the chosen direction intersects a face of the target object.
The faces in the target object must be all triangles.
