I've created several Reference Editor IDs in a holder cell in the CS. I'd like to link them to base object IDs. But when I click Edit Base in the Reference window and change the ID name to a base object that already exists, I get a message, "Form's ID is not unique! Previous form type is type NPC." Of course it's not unique: I'm trying to link the two together. And the previous form type was a type NPC, as well. How can I accomplish this? There are times when the CS seems a real pain.

What do you mean "link"?

To place a base object as a reference in a cell, you drag the base object out of the list on the left and drop it in the render window.

That makes it a reference, and you can give it a new name.

If you are trying to change an existing reference to a new base object, then you pretty much have to remove the existing and place a new one, I think.

Has to be another way to do this, because the mod I'm expanding has 256 NPCs lined up in groups of 64, in very nice squares. If the original modder had dragged each one by itself and placed it in the render window, I don't think his sanity would have survived. There had to be another way to revise them, too, because he indicated in revision notes that he'd changed them over from several base objects before to new ones, it can be done. What's more, all 256 NPCs are associated with just 4 base objects. I just don't know how he did this, and he's no longer part of the modding community.

Start from scratch.

Place one NPC and duplicate it (Ctrl-D).
Drag the copy to the side holding the Y key (so it keeps aligned)
Select both, duplicate and drag. Now you have four
Repeat a few more times (8 - 16 - 32 - 64) and you have the 64 identical NPCs aligned as you whish

It appears you can change the Base Item in TES4Edit, but I don't think I've seen a way to do it in the CS.

Create a duplicate of the base item, yes, but not change to another pre-existing one.

Yeah, I figured while thinking about it a short while ago that it must be possible to duplicate the base item, or Reznod wouldn't have been able to create all those mannequin clones out of a few base objects. in that case, I have to wonder how Reznod set up his large, perfect squares of 4 groups of 64 mannequins, because that makes using the holder cell a lot neater and easier to work with: less crowding. Any ideas on that?

grid snap?

Perhaps. Thanks--it's worth a try. The sheer size of the area Reznod set aside, plus the openness in all directions save for a floor, means you could easily drop 50 mannequins in such a way that although they look nearby, they're actually quite scattered. He must have intended to add a lot more mannequins, at one point, probably of other types--perhaps in version 1.0, when he was still using flesh-toned races.