Hi Jimski
1. Currently this is not supported and Diagram doesn''t even look at line intersections, but I did follow up with the Essential Diagram team and they have asked me to go ahead and log this as a feature request for consideration in a future release.
2. You can do this by using layers.
Here is a sample in which Symbols and Links are created in different layers and the Symbol''s layer is higher in the Z-order ensuring that Symbols are on top of the links.
Regards
Arun