Why are Nested Links showing up in VGO when there is no nested linked file

[rchernoffL4J9Q]

I have recently been struggling to understand something and I am hoping someone can help me. When I link a Model (I am going to call it Model B here) into my model A, there is another , 3rd model that shows up in V/G Overrides underneath the "Revit Links" tab, under the (+) sign, as though there was a nested model inside Model B. I know for a fact that there is no nested model, because I made the linked Model B, and it is not linked to any other models. The nested link is called 1(<Not Shared>) in the V/G Overrides.  When I turn this nested model off by unchecking the box next to it,,  all the elements in model B disappear, even though the box next to the linked model above it is still checked. This leads me to believe that the nested model showing here is  controlling the model above it.  I noticed this behavior in a different, more complex model, so I made a set of 2 demo models to be sure. There are only 2 models, the main model A, and a model B which is linked into Model B. So what is the model showing up as "1(<Not Shared>)" in the V/G Overrides? Why is Revit behaving as though there is a nested model, when there is no nested model? And why is this unknown nested model controlling the model above it? Anyone have any insight into this?

[Alfredo_Medina · Accepted solution]

What you see is not a "nested model". It's a list of the instances of each link. Even if there's only one instance, this dialog box uses a "tree" structure, similar to the project browser. Each link has a "+" sign, and when there is only one instance of each link, you see only one "branch".

Suppose that you have a project with multiple instances of the same link (a group of identical cabanas at different locations, for example). Then Revit will show something like "Cabana.rvt" as a "folder" with several "branches", one for each cabana. And each instance will show the following: Name property of the link (a number), then the name of the shared coordinates or "not shared". For example, here I copied my Electrical link somewhere else: then my 1st instance shows that this is link name "67" (which does not mean I have 67 links, it's some name that Revit assigns), and this first instance is using shared coordinates. If I copy that link somewhere else, the list shows a second instance, with a different name (number 82), and "not shared" as its location.

Using those check marks, I could turn on or off any "cabana" from the list. Or I can turn on or off all the cabanas if I use the master check mark at the top of the list of each link.

[rchernoffL4J9Q]

Thanks @Alfredo_Medina . That makes sense. I was unfamiliar with this as I never have more than 1 instance of a given link in a model. I always assumed that was bad practice, but I can see now how it would make sense in some situations.  I was able to figure out last night after experimentation that the number Revit ascribes to the "branch" is the number of times you have unlinked and relinked the same link. So when I linked the model for the first time, it was a 1(<Not Shared>). After I removed the link and relinked it again, the number was a 2(<Not Shared>) and so on. It would be helpful if the Revit API called these "Instance 1" instead of seemingly random "1(<Not Shared>) but here we are. Anyway thanks for taking the time to answer my question 🙂 

[Alfredo_Medina]

Glad to be helpful.