A hashable struct key for a TMap cannot be seen or modified in Blueprints

TMaps that use hashable structs as the key cannot have the key set for an element that is added to the TMap in a Blueprint. A default value is set, but it cannot be seen or modified.

1. Create a new Basic Code project.
2. Add a new Actor code class to the project.
3. In the header file, add the following property to the body of the class:

   UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = TestCat)
   TMap<FLinearColor, float> MyMap;
   

4. Create a Blueprint based on the new Actor class.
5. Locate the MyMap property in the Blueprint.
6. Add an element to MyMap.

RESULT:
The value of the element can be set, but the key is not visible or editable.

EXPECTED:
The key is visible and can be set by the user.