Dyalog currently support the ‘help’ event (400) on most objects, but there is no easy way of providing the help in the approved Windows style. This function can be set on the ‘Help’ event handler of any object, and passed a vector of text vectors to show as the help panel:

Help : ¸ #.Win.WhatsThis 'Press to change date'

Note that the shadow effect is not quite perfect! Hopefully this function will be superseded by an appropriate internal call one day.