Hardcoded SelectionElementName

If in DataTemplate for Link (and maybe for Node, not tested) change the go:Part.SelectionElementName from “Path” to another name (and change go:LinkShape x:Name too) then SelectionAdornmentTemplate don’t execute.
For example if in the DraggableLink.xaml change DataTemplate to

<DataTemplate x:Key="LinkTemplate">
  <go:LinkPanel go:Part.SelectionElementName="Path0" go:Part.SelectionAdorned="True"
                go:Part.SelectionAdornmentTemplate="{StaticResource LinkSelectionAdornmentTemplate}"
      <go:Route Routing="AvoidsNodes" Curve="JumpGap"
                RelinkableFrom="True" RelinkableTo="True"
                LinkReshapeHandleTemplate="{StaticResource LinkReshapeHandleTemplate}" />
    <go:LinkShape Stroke="Transparent" StrokeThickness="5" />
    <go:LinkShape x:Name="Path0" Stroke="Black" StrokeThickness="1" />
    <Path Fill="Black" go:LinkPanel.ToArrow="Triangle" />

then selected link will not be draw with DeepSkyBlue color.
Simple question: Why?

Yes, the “Path” element name is hardcoded for use by the LinkPanel and Link classes.

It the Path element name is hardcoded then what does <span =“Apple-style-span” style=": rgb248, 248, 252; ">SelectionElementName property means?

That property simplify identifies which FrameworkElement in the Part’s visual tree is supposed to get the selection handle when the part is selected. It’s not needed if go:Part.SelectionAdorned=“False”.