Preventing tab key to navigate in widget buttons

Hi, to disable navigation at all (or to modify it), you can use this C++ code:

	TSharedRef<FNavigationConfig> navigation_config = MakeShared<FNavigationConfig>();
	navigation_config->bTabNavigation = false;
	navigation_config->bKeyNavigation = false;
	navigation_config->bAnalogNavigation = false;
	FSlateApplication::Get().SetNavigationConfig(navigation_config);