Having the open / close ( expand / collapse ) button for the tool container in lhe top right corner implies that everytime a big container is expanded, to close it the user has to move the pointer to its new position, which sometimes mean scrolling / zooming out and then zooming in to locate it.
I suggest to locate that button in the top left corner by the side of the enable/disable switch or even a double click mechanism for open/close, which would enable to user to open, see what is inside the container, and close it without moving the mouse to locate the new location of the button.