Is there a condition that checks if a certain map marker is discovered?

For example, a dialogue option is "Let me take you to this place" and the response would be.
"First you need to find this place" - if the marker isn't discovered, and
"Let's go" - if the marker is discovered.

Is there such a condition or do I have to script it?

With OBSE you can do:

if mapmarker.isMapMarkerVisible && mapMarker.CanTravelToMapMarker  ; the marker has been discoveredendif

This is not something you can do directly in dialog conditions, though.