Sorry for the delay, due to the release of the 4.5 version products, the development teams could not dedicate time as usual to the discussion forum. Today was published a new Code Community sample that shows how to drag and keep the vertices selected. It is a little bit short of what you are trying to accomplish overall but I think that it will help you to see the code and the comments on the inherited class of EditInteractiveOverlay in that sample. Please, check it out, Select Vertices,
wiki.thinkgeo.com/wiki/Map_Suite_De...ys_Samples
We will continue in the Code Community on that theme, and we will publish shortly one sample that shows how to select and drag vertices as a group.
Thank you.