"New Outlook" won't let me change meeting reminder times.

[CapinWinky]

I just turned on the "New Outlook" toggle to try it out and noticed that I can't change the reminder for a meeting from 15min before to 30min before without sending a meeting update for meetings I created. There is no save button and closing the window discards the change. 

I thought that maybe I could edit the ribbon to add a save button, which was the solution to this kind of issue in older versions, but I can't find anywhere to edit the ribbons either.

For meetings that I did not create, the meeting window just goes black when I change the reminder time.

[#2]

@CapinWinky 

I am an independent advisor answering New Outlook Questions.

During this investigation, I changed the reminder from 15 to 30 minutes without any issues, and the Save Button was available in the event.

Last week, I was experiencing some issues.  I tried the following:

• I reverted to Classic Outlook and relaunched New Outlook.
• If it persists, I double checked the behavior in OWA.
• If it is working properly in OWA, then contact Microsoft Support.

If you find this information helpful, please mark it as the best response or like it, which will assist others with the same question. 

[#3]

I pinned new Outlook and reverted to classic, then launched new Outlook with classic also open. Making a test meeting, I now do have the save button. The reminder setting doesn't appear for me in the area you highlighted, only in the top ribbon (also in your screen cap).

Attempting to change the reminder setting in meetings others created still causes the entire meeting child-window to go completely black. Closing that window by clicking where the `X` should be (or via the taskbar) also causes the calendar to stop displaying the meeting. Changing the calendar view (from week to work week, for instance) will cause the meeting to reappear, however subsequent attempts to edit it open directly to the blacked out window until new outlook is completely closed and relaunched. The change to the reminder setting is saved.

I thought the blackout window was a dark theme thing, so I switched to light theme and got the same behavior, except the fill color became an off-white instead of black.

EDIT: Changing the theme from light to dark allowed me to open the meeting window for a meeting created by someone else again, after it had already gotten stuck with a whiteout window. Changing the reminder time again just caused the blackout window issue again.