Comment 7 for bug 1503910

The floating state of the panel is persistent. It only needs to be set to floating once. From then on it can be opened with cmd+t only for the rest of time, the float button never needs to be clicked again.

I fail to see how cmd+t closing the panel whether it is anchored or floating would "create chaos". But if you are concerned about cross contamination and want to treat it as an independent window instead of a detached child of the main window then the user should be able to close it with the standard cmd+W just like any other window at least. To not have any keyboard-only way to close a window is bad from an accessibility standpoint alone. I don't think it's as intuitive as cmd+T for open and close but it does need some way to close via the keyboard.