I started using the Timeline Group function for the first time today because I got tired of scrolling the timeline. After creating a group, I wanted to move other items into it. You can't drag and drop and there's no edit option:
You can't perform directly change a group as I discovered from reading the forums. You have to delete the group and regroup the items. It isn't ideal but acceptable.
To my horror, however, it is done by using the "Delete" command in the menu. I didn't consider it because I feared it would delete the group and its items. It requires a leap of faith that it will do what you want, not what you fear. Clearly, this is a form of faith based UI and classic mystery meat:
According to the Macintosh UI guidelines, a good UI makes it clear what items a command will operate on based on the current selection using highlighting as an additional indicator. Moreover, if selecting the command will require additional parameters as in a dialog box, for instance, the command's title should have a leading ellipsis ("Delete...").
