Link selection

After I put selectionAdornmentTemplate to link when selecting link I now have situation like in picture. Is there easy way to have link selection over link line instead of this blue rectangle or at least to remove rectangular selection and then manage that manually through data binding of strokeWidth and stroke color regards isSelected property of link?

Did you see the example in GoJS Selection -- Northwoods Software ?

Or the definition of the default selection adornments in in the setupSelectionAdornments function?

I think you’re missing instructing the Adornment to treat your Shape as the path element by setting GraphObject.isPanelMain to true. GraphObject | GoJS API