I think you can use AttributeManager to wrap the URL in an href tag something like:

<a href="https://www.safe.com">link</a>

or for an attribute it would look like:

<a href="@Value(DWNLD_URL)">link</a>

Still having trouble, not sure which part of the formatting I should do in kmlproperty setter vs attribute manager. If I include the attributes in kmlproperty setter I can do any formatting in attribute manager. (i think). Ultimately I want my popup balloon to look like the attached one, no grey line on every other record, and then hyperlnks on certain records.