If a custom component creates another component in code, the second component does not appear in the hierarchy inside the blueprint menu. It does appear in the hierarchy for an instanced version of the blueprint already placed in the level.
MyScene shows up in BP editor but MyMesh does not.
MyMesh does show up in hierarchy (like it does for instanced blueprint in the level).
Head over to the existing Questions & Answers thread and let us know what's up.