Add calendar status to indicate immovable vs. moveable meetings/appointments
For many people there are two types of meetings/appointments that both show as busy today:
Items that can easily be moved as-needed (e.g. some 1:1s. meetings with a small number of attendees within the same team, time blocked for a specific activity that can be done at another time, etc...) A tentative status typically doesn't for these items since the time really is for a committed appointment/meeting, it's just that it's moveable if needed.
Meetings that are not easily moved (e.g. a meeting with a skip-level manager or key customer, a meeting with a lot of people that are difficult to schedule, etc...). An out of office status typically doesn't work for these items since you are actually in the office. Any new meetings booked during these timeslots will almost certainly be declined and have to be rescheduled.
Outlook should clearly differentiate between these two statuses in order to make it easy to book meetings with people that have very busy calendars and empower people to set aside truly meeting free blocks of time that are not easily infringed on. This would also help individuals easily identify which meetings on their own calendar are the most important and also identify meetings that can be moved to free up focus time/have other meetings/use for personal reasons like doctor's appointments.
In addition to helping individual users, this would be particularly useful for people that manage other people's calendars.