Markers for links appear when you turn on the Markers control in the View Attributes dialog. The marker icon is different for different link types.

The Mini toolbar for the marker is displayed when you hold the pointer over a marker. The Mini toolbar for links contains tools for opening and removing links, and editing link properties. Also, when you hold the pointer over a link to an external file type such as jpg or pdf, you can see the preview image of the file in the Mini toolbar.