How to use existing interfaces in type libraries in other type libraries as the type of new properties.

There are many type libraries introducing lots of interfaces like _connection in ADODB_TLB.pas and I want to use such interfaces as the type of a property of an interface in a new type library.
But I have not found any way to add these existing interfaces to the available types in the corresponding combo box in the type library editor. I know interfaces in the referenced type libraries will show up in the type combo box but I don't know where to introduce these referenced type libraries. I would be very grateful if someone help me to manage the task.