MagicDraw/Cameo: You and can drag-n-drop the icon for most Diagram types from the model browser onto a symbol in a Diagram to make it the default hyperlink for that Element; clicking on that Element symbol will then open up that Diagram.
MagicDraw/Cameo: supports HTML hyperlinks directly on model elements, and they are launchable from model element symbols in diagrams.
MagicDraw/Cameo: supports HTML (including hyperlinks) in String based tagged value (Stereotype property) fields. Just activate HTML mode during tagged value editing.