Yes, essentially I have removed the transform manager's selection capabilities. I capture mouse down myself and then tell the transform manager what to select / deselect based on the results of my testing. We've made several other modifications to it, as we needed to control the parent where the items are added as well, so there's a bit more to it, but a simple solution would be to just do what I've suggested. Override the select/deselect capabilities and then code a mouse down event for your own purposes.