Re:Inspector "Properties" Window
actually now that I'm home, I understand you're likely not talking about collapsing the whole inspector window, but getting the properties window closed.
click on the TRACK or CLIP button at the top of the window. if the track properties are open, clicking on the track button will close it, if the clip window is open, clicking on the clip button will close it. clicking on the one which is not open will only open it.