I am using Outliner 5.15 on macOS, and am trying to drag a header with some childrent to another parent. I feel like I have done this a million times before, but I am not able to do it anymore.
When trying to drag, it looks like I can only select.
You have to grab it from the Row Handle, which (depending on whether or not there are children items) is either a small dot at the left side of the text, or a disclosure triangle.