Rounded corners and transparency

Feature request to have rounded corners on main window and to have adjustable transparency on main window or optionally file display background (see through to desktop). Have minimum level of around 10% so as not to make invisible.
Additionally adjustable blur please.

The window has a standard frame provided by Windows, so it will have rounded corners if the OS has rounded corners.

(In other words, rounded on XP, Vista, 7 and 11; square on 8 and 10.)