To do Alt + H + A + O on Mac in PowerPoint, download and install Accelerator Keys, then press Option, followed by H, A, then O.
Command: Promote (Decrease Indent)
This is how to do Alt + H + A + O on Mac in PowerPoint with Accelerator Keys, the native ribbon and alt key shortcut solution for Mac users who get more done with PowerPoint.
Alt + H + A + O promotes the selected text or decreases its indent level, moving it to a higher outline level. In bulleted lists, this moves items up one level in the hierarchy.