Polytonic Greek on-screen keyboard

Writing classical greek on a physical Danish keyboard or an on-screen standard Greek keyboard is not difficult provided you define the keyboard as Polytonic Greek. It is unfortunate that there is no on-screen polytonic Greek keyboard. The main problem whether you use a physical or on-screen keyboard is remembering where the diacritics are. An on-screen polytonic Greek  keyboard showing where the diacritics are, would be a lot easier to use. Only the graphic display would need to be changed compared with the standard on-screen Greek keyboard.