On a Mac computer an active window has three dots at the top left corner. The most left one is red and is to close the window.
The Customize Backlight window has those three buttons as well but they are not working. This means that the window can not be closed by clicking on the leftmost button. It can only be closed by clicking on the “close” button at the bottom right. Not a serious thing but perhaps it can easily be fixed.
Bert