Dynamic Delegate for Actor doesn't show up in BP Editor

The delegates for actor should show up in the Detail tab like components. There should be an "Event" group and list all available delegates, and designers can click on the "+" sign to add event on the graph.

It's very confusing since the exact same steps work properly for ActorComponent and its children classes.

1. Declare a dynamic delegate signature: DECLARE_DYNAMIC_MULTICAST_DELEGATE(FMySimpleDelegate );
2. Declare a delegate in an Actor class:
UPROPERTY(BlueprintAssignable)
FMySimpleDelegate Event0;
3. Compile, and create a BP version of MyActor class
4. Try to find the delegate inside BP editor.

Results: The newly create delegate "Event0" doesn't show up in Details tab.