Oh, thank you. Very precious remark.
It explains a lot. Than is why they reappear once SU restarted.
Silly of me.
The very beginning of the problem has been once I have noticed that after some shortcut manipulation (see below) the functionality of SPACEBAR + SHIFT + W (and UpArrow) has stopped working with Lumion.
Prior to that issue I had assigned CTRL+SHIFT+W and E, CTRL+SHIFT+P to a Logitech MX mouse buttons.
As far as I recall this has been my only change I have made.
Should it be any Windows hotkey conflict?
Same keyboard disfunction I have got with Alienware Macro keys working with Lumion.
In this case the macro keys SPACEBAR+SHIFT and SHIFT do not work.
Once more thank you very much for your valuable explanation.