Creation kit not letting me pick map markers for locations in Solsteim

[GameWyrm]

So, I'm making a house mod that takes place in Solsteim, and I've created a location in the exterior cell. I tried to set a map marker for the location, but to my surprise, I'm unable to set the World Location Marker Ref to any object in DLC2SolsteimWorld. I'm not sure if this would break anything, but I'd like to know how to fix it if possible, as I believe that this is also the cause of another issue I'm having that prevents the house from being compatible with "Hearthfire Multiple Adoptions."

 

I am using Skyrim Special Edition 1.5.62, Creation Kit 1.5.3, and SSE Creation Kit fixes 1.7.