In the MIDI Devices editor, edit is a long click, and open is a short click.
On a Controller in the Controller editor, edit is a long click, and select is a short click.
On an Action in the Controller editor, edit is either a short click or a long click, select Edit.
In the Layout editor, to edit an item is a short click. Long click does nothing.
That last one confuses me, and I find myself sitting in a long click, waiting for it to open. I think it should be like the Action editor.