If a Component/ variable is given a custom category in code, using the HideCategories specifer inside the UCLASS macro does not hide the category.
1. Open UE4Editor (code project)
2. Add code to project based on Actor (MyActor)
3. In the MyActor header file add the following:
UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = TestHiddenCategory)
float number;
4. Inside the UCLASS macro add the following
HideCategories = (Actor, Render, TestHiddenCategory)
5. Compile
6. Make a blueprint based on MyActor (MyActorBP)
7. Add instance of MyActorBP to the level
Result:
Actor and Rendering categories are missing (hidden) but TestHiddenCategory is still visible.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-19743 in the post.