Mutable: Child parameters hidden when intermediate Object Group uses "All Options"

FCustomizableInstanceDetails::FillChildrenMap() unconditionally registers parent-child relationships via __ParentParamName metadata without verifying the parent exists in the active parameter list. When an intermediate Object Group uses "All Options" (COGT_ALL), no UI parameter is generated for it, yet its children still reference it as parent — causing the rendering loop to skip them (they have ParamHasParent = true) while the parent is never iterated to draw them recursively. Confirmed unpatched in both UE 5.7 and UE5Main.

Fix: Add an ActiveParameterNames check in FillChildrenMap so that parent-child registration only occurs when the parent is present in the drawable parameter set. See CustomizableInstanceDetails.cpp:914-925.

void FCustomizableInstanceDetails::FillChildrenMap(int32 ParamIndexInObject, const TSet<FString>& ActiveParameterNames)
{
  const UCustomizableObject* CustomizableObject = CustomInstance->GetCustomizableObject();
  const FString& ParamName = CustomizableObject->GetParameterName(ParamIndexInObject);
  FMutableParamUIMetadata UIMetadata = CustomizableObject->GetParameterUIMetadata(ParamName);
 
  if (const FString* ParentName = UIMetadata.ExtraInformation.Find(FString("__ParentParamName")))
  {
    // FIX: Only register as a child if the parent parameter is actually going to be drawn
    if (ActiveParameterNames.Contains(*ParentName))
    {
      ParamChildren.Add(*ParentName, ParamIndexInObject);
      ParamHasParent.Add(ParamIndexInObject, true);
    }
  }
}

1. Create a hierarchy: Body CO → Head CO (Object Group) → Acc CO (Object Group) → AccParam (Float Parameter)
2. Set Head Object Group's Group Type to "All Options" in Body CO
3. Set Acc Object Group's Group Type to "Toggle" in Head CO
4. Compile and open the CO/COI Details panel
5. Expected: "Acc" and "AccParam" are listed
6. Actual: "Acc" and "AccParam" are completely missing