The markup of Recurrence editor does not provide IDs out of the box for easy widgets selection in it. Here are some unrefined selectors based on the Scheduler Index demo configuration:
// Start DateTime picker
var startDateTimePicker = $('body > div.k-widget.k-window > div.k-popup-edit-form.k-scheduler-edit-form.k-window-content.k-content > div > div:nth-child(4) > span.k-widget.k-datetimepicker.k-header > span > input').data('kendoDateTimePicker')
// Repeat DropDownList
var repearSelector = $('body > div.k-widget.k-window > div.k-popup-edit-form.k-scheduler-edit-form.k-window-content.k-content > div > div:nth-child(13) > div > span > input').data("kendoDropDownList")
// Recur on day of the month numeric textbox
var recurMonthDay = $('.k-recur-monthday.k-input').eq(1).data("kendoNumericTextBox")