Edit Meeting Time and Details within Teams
You should be able to open an existing Teams Meeting, and make edits (to content, title, time, duration, and recurrence details ) if you are the organizer (or if Team distribution list is the organizer).
The only edit I think you currently cannot make, is that you cannot add or change a channel
Rachael Conley commented
As a user, you can actually do this today! Simply open the meeting invite in Teams and select Edit in the window to make changes. You can make changes to one meeting or even the whole series if it is recurring.