I have a BT keyboard in use with my L5. This keboard has a key labeled with “Win” (the so called Windows key) and printed above “Win” is a small letter symbol in blue, which means if I do use the blue Fn + Win it will launch a mail application, which works fine, it launches a terminal app and inside mutt as MUA. Perhaps I have configured this somewhere as the default mail application, don’t remember at the moment. So far so good.
When I press only the Win key, it gives the same result as I would use the arrow on the screen button to slide the actual app to above and give access to the desktop. Pressing it again, slides the app again in main view. This means thar any app itself will not get delivered the keypress of the Win key, because it is catched by Phosh(?). Where is this configured and how for example the terminal app urxvt could see this key and make use of it?
And that is the key to understand your issue. Did you install a windows app for this keyboard on a windows to config this? Did you write it in a keyboard internal storage? Did you config something somewhere on Linux? And even better asked: what keyboard are you actually using?
And the Win-key gives all default actions to manage windows (yes, even on Linux). You cannot only minimize and maximize the current app, but also switch between apps (Win+Tab) or repositioning windows (Win+ArrowLeft/ArrowRight) etc.