Currently it is only partially possible to edit nested component subobjects, but not in a way that's consistent with how top-level component subobjects are edited (both Blueprints and IWCE). This is causing issues for users who want to allow defaults to be edited within these instances.
This one may need some discussion as to how to properly visualize nested component subobjects within the overall hierarchy that's owned by an Actor instance. Currently, all nested subobject attachments are simply being excluded from the tree view in both the Blueprint editor as well as in IWCE.
Additionally, subobject references are currently exposed for editing in the Details panel as reference properties with editinline characteristics - in this way they can be set to NULL, which is more in line with asset references and not subobject references. Users should not be able to just NULL these out. There are some other issues with exposure in the Details panel as well (outlined in the attached UDN link).
1. Open the editor
2. Create a new C++ class based on Scene Component
3. Add this code to the .h
4. Add this code to the .cpp
6. Back in the Editor, create a new Actor Blueprint
7. Add a component of the type created in step #2.
8. Notice that the nested 'Box' component does not appear in the tree view.
9. Notice also that the details for the 'Box' component are editable as part of the custom component class type, with editinline characteristics.
Expected result: Nested component details are editable through the components tree view, and are not editable as editlinline properties in the Details panel.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-33878 in the post.