Enuf chit-chat, all you have to do is move your mouse pointer over ANY already shown column, but over its very top, over its name. Once there, just click with your right mouse button, and select the desired columns with the left button.
Once done, you can easily drag-and-drop the columns to change their order, or pull their ends to change width. After setting, it is recommended to close and reopen the hub frame, so your preferences will be saved. Please see also the attached screenshot. In my case User list is horizontal, this does not change a bit.



