How do I make inlets from the engineering available for use under feature definitions nodes?

The inlets listed in the library need to have a corresponding Feature Definition - the Feature Definitions stored in a DGNLIB is what you see when placing a node. (The node will also have the symbology, and 2D/3D cells defined.)

Hi Mark Marnell, the inlets do need to have a corresponding Feature Definition. The challenge is that there is no property allowing for feature definition to be created in the Engineering Library for inlets. Please see image 1, the list of properties for the selected inlet doesn't have a property for feature definition.

The feature definitions are stored in a dgnlib ('SU_Features_Annotations_Levels_Elem Temp UK.dgnlib' in my case) not in the engineering library. To me, the engineering library only stores real life data.

You need to edit your DGNLIB and create the feature definitions you want. In my current workspace, I only have the following in my Inlets, but the engineering libraries list many more. The enginerring library is NOT where the feature definition is defined.

I agree with the above reply. But after I have created the feature definition, how do I link it back to the invert items in the engineering library since the feature definition properties also doesn't have a "key/ID" property for inverts in the engineering library i.e. how to i create a relational database link between feature definitions and the engineering library inverts. 

You will need to create a corresponding prototype to the inlets you desire to use. So the whole path to get to a Feature Definition from the libraries is first import the inlet in question into an Inlet Catalog entry, then to a Catch Basin Prototype, then to the Feature Definition.