I've noticed a bunch of conflicts in SSEEdit regarding this line and I also wondered what it actually does and if it has any impact on the game at all.
Some mods that influence worldspace (such as Plockton's Culling Data Glitch Fix - meant primarily for the huge square hole in the Sea of Ghosts), have this line empty. I left it empty on one setup and I didn't have any weird stuff going on. On the other hand, the mod Convenient Carriages for example has this data populated (with some sort of technical gibberish I don't understand), and when I did the setup with this data, there weren't any problems either.
I also noticed that DynDOLOD esm and DynDOLOD esp have different MHDT values; esm is the same as DLCs, but esp follows the value set by the load order. I really don't know what to make of it. I didn't notice any particular issues - although that might be because I don't know what I'm looking for.