Why should you merge your widget managers?
The managers only care about their own layers. Layer from other components are ignored, that can result in unwanted behavior, for example mouse cursor removement, although this is still needed in another layer.
Step 1 - Add new Layers
Step 2 - Replace Functions
Replace all functions (GetWidgetManager, Open, Close layers etc.) with the functions of the component you want to use.
If you want to find the functions you want to replace and delete, you can rename it and use unreals search function to find it. (See Image)(You have to save all before finding it, otherwise it will not find the new name)
Step 3 - Delete the Widget Manager
Remove the widget manager from the controller and rename it. (If you dont rename and save it, it will still be shown as referenced because the name is the same.)
After that you can delete the widget manager folder of the component where you replaced the functions.
Do NOT delete assets that are still have actor references, replace them before attempting to delete again.