Finally it worked for me. I logged in into Webmail outlook of my organisation and deleted that folder having clock/scheduled mark on it. As I understand this solution does not work for everybody. Perhaps there are some specific pre-conditions or circumstances when solution works or doesn't. In anyway, I made that folder scheduled from Outlook app in Android phone. The folder was empty. I hope it helps to somebody.
Shame on you Microsoft with all your poorly implemented functionalities and incorrectly handled object properties.