Ok I'm pretty new to Bethesda world making but I seem to have found a bump I cannot scale:
When I'm texturing the height map for the world space I have the landscape window with all the textures in game. However, depending on where I am on the World Space, some textures don't load, and therefore appear as black. I'm wondering if there is a way to edit which textures are loaded in a cell? I've been scouring the wiki but it really has no relevant information. I'm also pretty sure that when I hear the answer I'm going to hit my head on the desk for how stupid I am.

This should be in the Creation Kit board I think. Every cell can have five textures in use I believe... You can double click the " i " key in a cell and you should get a list of textures in use and remove some. Not sure if the black texture appears only if you use more than five... It might be a bug. I've seen it many times when working with my worldspace.

A world cell is divided into 4 parts. Press I and you can see a list of textures used for each partition of the cell.

If there are 6textures in 1 partition then that partition will not render any more textures. Meaning when you try and paint new textures they simply appear black. So on this menu you can remove one of the 6 textures. I recommend removing the one that is least used.
And that should free up 1 more texture to be used.