If you have an existing assembly within your product hierarchy, and you want to convert that assembly into a parts category/hotspot on your 3D model, rather than having the assembly sit under a separate parts category/hotspot, simply enter “Yes” into the Combine Assembly with Lowest Level Category column in the row of the desired assembly.
The assembly will retain any sales content (description, price, etc.) that has been applied to it via the Sales BOM but will gain a hotspot on your 3D model.
It is important to note that this will only apply if the category/assembly is at the lowest level of the hierarchy, ie, no further parts categories are contained within the assembly.