Any one know if, when you Finalize the NavMesh in a cell you modify the NavMesh for, does it change the Navmesh record in adjacent vanilla cells that border it when they synch up (even though you do not touch them)?
Thanks

It doesn't.

Actually it does, and it's necessary to update the border data. Though if your edits are far enough away from said border, you could get away without re-finalizing the navmesh unless you added a door.

The OP asked about exterior... so no door involved. When I checked my navmesh edits outside Whiterun (cell 4,-4) and finalized the cell, the surounding cells were NOT flagged as edited. If I change a border navmesh (where the green border line shows), then it does indicate the bordering cell was edited. But if my navmesh changes are isolated to just internal (no border) triangles, I don't see bordering cells being flagged as edited.

Save your plugin and then reload. You'll find your situation has changed, just as I said.

You'll have a total of 5 cells edited from finalizing one. One in each direction from the cell you're in. Thankfully it won't edit the cells diagonally on each corner though.

An exterior cell can still have a door btw, just because one doesn't say there is doesn't make that advice any less useful. If you aren't adding a door and all you do is move some triangles that don't directly touch the border, you don't need to re-finalize. Then you'll only have one cell of navmesh edits instead of 5.

Okay, one hard CK crash later and yes, when I save and reload I see the changes.

OK, then those are not dirty edits then.

Also - it seems like it will crash the CK if you try to delete (ignore) (in the data details tab )those changes in the cells neighboring the one you edited the Navmesh and finalized on.

That's been my experience as well.

Yes, because the NAVI record is expecting those forms to be listed and when it doesn't find them, things explode.