So, I'm in need of modifying one of the base collision layers. I see that I can create my own in the CK, but in NifSkope, when selecting the OL_ collision layers, you have a drop-down to choose from with only those defined choices.

Is there a way to get a .NIF to see a newly created collision layer created in the CK?

http://imgur.com/CN3MA that seems to correspond with the collision layer, for reference.

Probably. Best to ask the http://niftools.sourceforge.net/wiki/NifToolsguys.

Thanks, will do.

I sorta made some progress. A collision primitive of layer L_LOS has the properties that I want (collides with clutter items, but not the camera, the player, other actors, spells, or the ability to pick up an item through the collision primitive). However using the NIF-selectable layer OL_LINE_OF_SIGHT, which I figured would be the same thing, isn't quite. It collides with clutter items, the player, other actors, and the camera, but not spells or the ability to pick the item up through the object. Strange.

Semi-related question even though I almost positively know the answer is no: Is there any way to duplicate a primitive at run-time? I can make a primitive do what I want, but I need to be able to create n number of them at will, and when creating a new instance of the primitive's base object, it has no spacial dimensions and no way to adjust its dimensions at runtime that I can see.

Very interesting work with custom layers in NIFs... I've only messed with custom layers in the CK (for primitives).

But about in-game primitives... I really doubt it since the width/height/depth needs to be adjusted, and I never found a script function that can do that; nor do I know of a function that can make copies of a REFR - only baseObjects (which is why it would need resizing).

A potential workaround I discovered while decoding the WATR data structure is to use a custom water object... they can be set to trigger spell effects/etc when something enters them, play sounds, all kinds of stuff. I don't know if they can be dynamically created or moved though - it'd have to be tested.