Manages custom nodes for the Visual Script editor. This singleton can be used to manage (i.e., add or remove) custom nodes for the Visual Script editor. Add a custom Visual Script node to the editor. It'll be placed under "Custom Nodes" with the [code]category[/code] as the parameter. Remove a custom Visual Script node from the editor. Custom nodes already placed on scripts won't be removed. Emitted when a custom Visual Script node is added or removed.