If an EditorWindow is shown via ShowAsDropDown, both right-click & middle click are not detected using e.g: Code (csharp): rootVisualElement.RegisterCallback<ClickEvent>(ce => Debug.Log("Clicked: " + ce.button)); Left-click is detected fine. For 2019.4 RegisterCallback<MouseDownEvent>() works fine for both. I believe this should work and does not (tested 2020.1.2f1 & 2020.2.0b2). Is there any work-around in the meantime? Many thanks in advance.