The trick to moving the window into a docking port is the cursor. I was trying to control getting the docking port to open, with the corner or edge of the window I wanted to dock there.

What actually controls the docking port is the cursor. When I put the cursor on the window's title bar to drag it to a docking port, when the cursor hits the dotted line denoting the docking port, the port opens!

I hope this will be helpful to others.