The Menu Bar on Lr6.6 is different to all my other applications in Windows 10: it is grey (not blue) and it doesn't have the familiar minimise, maximise and close icons at the top right.
To close Lr6.6 I have to use Ctrl+Q or Alt+F4.
Some keyboard functions are not to Win10 standards:
Windows+left and Windows+right do not work,
Windows+up and Windows+down do go between full-screen and a window but the window size can not be changed by click-and-drag.
How can I rectify this?
Just discovered the answer myself: Shift+F (Menu Bar disappears completely) then Shift+F again and the Menu Bar is back to normal.
Sorry to have troubled you.