TextMesh Pro How to change link tags using FindIntersectingLink?

I have implemented IPointerClickHandler with FindIntersectingLink to process dynamically created links. This works well but now I want to change the (plain) links to underline on mouse hover.

I watched the video "TextMesh Pro - Link Tag Support & Tracking" but only vertex color was addressed. I don't know how I would do tags because they exist outside of the link.