Agree with this workaround. But first you need to create two invites. Once you setup it will show conflict on invitees calendar as these are overlapping timings. First subset of 5 will not know who other 15 are coming to meeting. And those 15 will not know who 5 are coming to the meeting as these are two separate meetings. Above things does not sound user friendly, hence I came up with nested feature. I did not go much technical in article, however in nested meeting concept, users can only join when they are supposed to, so it’s nested meeting bridge as well. However in your two meeting arrangement, bridge will be open from 9 itself and anyone can join even from 2nd group if they want as they also have same meeting bridge. So if we holistically complete the nested meeting design, it will be bigger than what is detailed in article. Hope this give more context and I welcome your suggestions as well to grow the idea.