Right now only native subobjects are displayed in the details panel with meta = (ShowInnerProperties) is set. Child Actor Components are an example of this, where if the child actor you have added has any blueprint components they will not be displayed.
Users would like it if BP added subobjects were displayed as well!
upd. According to Affects Version field, issue reproduces in 4.26, Regression for 4.27 - No.
1. Create an actor blueprint called "BP_Foo"
2. Add a point light component to it
3. Create another actor BP and add a child actor component to it
4. Set the child actor component's class to "BP_Foo"
Result: The Sphere Light component is not displayed anywhere
Expected: Any BP added subobjects are added in the details panel when editing the CAC and can have their components manipulated
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-129514 in the post.