You can set pickable: false on your white shape. But the space will still be pickable, since you have a red background on the entire Node. You will have to remove that background also, and make the TextBlock’s background red some other way. Something like:
Display in the preview only the Main Icon without the Label.
By “in the preview” you mean when dragging? How you are doing it is probably OK, but you should use opacity instead so that the object does not need to re-measure: