In a Revit Model Collaborated in Cloud (Model A), if you manage links and link to another Revit Model (Model B) set as attachment, then you link "Model A" into another model (Model C) you will see both Model A and the nested linked "Model B" in Model C as you would expect. This is called nesting links and is not a new Revit concept. All is well from a Revit Standpoint, however, if you publish "Model C" to BIM 360 with 3D views and sheets. You only see what is in Model C on the sheets and in the 3D Views, nothing from the nested links is visible once so ever in the BIM 360 Model Viewer. This is a considerable loss of function from the software. The workaround I am using is to Link "Model B" directly into "Model C" on a Workset that you toggle on to publish only. This is an industry standard workflow (nested links) and BIM 360 publishing should support this functionality. I hope this feature/function gets addressed in the product soon.