If you register a method with a non-void return type, you can use the value it returns as a parameter in later methods. Any parameter that matches the return type of a previous method will show the same [∞] button used to link event parameters.
This allows you to call methods with parameter types that aren't actually supported by UltEvents. After you select a method with a return value, it will be added to the list of supported parameter types when selecting the method for other listeners later in the same event.