ESL QuikStep will allow you to set breakpoints on statements in "on drag" and "on dragover" responses. However, if a breakpoint is hit during an "on drag" response, a drag will not start, because the ESL application will not have the focus (ESL QuikStep will have the focus).
Breakpoints are ignored during an "on dragover" response, because a drag operation is modal to the system, and the focus cannot be changed at this point.We may make a change in the future to detect that you are trying to set a breakpoint inside an "on dragover" response, and display an error at that time.
To debug "on dragover" responses, you will need to send messages to the errorlog. Use the -terp trace in your command line.