Is there a way that I can export or copy a specific custom-created cell from one plugin file to another? I ask because I messed up the overworld cell for my dungeon mod, and cannot figure out how to fix it. It seems like it would be much easier to just take the custom interior cell from the old .esp and put it into a new .esp - one where there overworld data hasn't been altered. Any ideas?

Open your mod, but DON'T make it the active file. Duplicate your cell with a new name, and save out to a new ESP.

Open the new ESP and check...it should have a completely new version of your custom cell.

Something I've been working on in the CK I would copy stuff from other cells.. or accidentally move something and it would show that I edited it when I didn't really do anything to it.... So I'm assuming since I touched it ... it will include that in my .esp?

So could I make a new cleaner plugin without those "edited" cells being included?
(via Redwood Elf's method)

I suggest you look into TesVSnip. Work with a backup of your file until you understand how to use it. It will let you snip out references to objects and cells that you don't want. It helps if you have assigned names to your objects that you intentionally edited. It also helps to have the file open in the CK so you can reference the items you are snipping as you snip them. In general, references to interior cells are in the Cells grup and references to exterior cells are in the World grup. Good luck.

Thank you Redwood Elf for that fix - it worked perfectly! Also, I will look into TesVSnip, so thanks for the advice ch0k3h0ld.