Well the description says so and I remember using it in Cyrodiil to show POIs on the map I have not discovered yet + delves + their bosses in the delves.
Code:
The following can be shown on your maps depending on your settings:
Wayshrines
Area of Interests
Public Dungeons
Mundus Stones
Dolmens
Group Bosses
Group Dungeons
Quest Hubs
Crafting Locations
Solo Dungeons
Group Events
Group Delves
Trial Instances
Install it, open the settings, go to POIs submenu and enable the dungeon bosses. It should apply to the delves as well then.
I don't know what these "Volendrung Spawn locations" are and I doubt an addon could show them dynamically.
You could just add them via Harvens Custom Map Pins then.