Mark Invites Private

I am an executive assistand and use OneCalendar to manage both my personal (Gmail) and work (Outlook) calendars on my iphone. As I deal with sensitive information, I often need to mark meetings private. As this is not currently possible on OneCalendar, I have to create the meeting in OneCalendar, then if it needs to be marked private, I need to open my Outlook app, open the calendar in that, navigate to the meeting, and use Outlook to mark the meeting private. I have unfortunately paid for a calendar app that does not have the features I use on a regular basis. At this point, I am regretting that decision.