Smartphone-style keyboard on Windows?
Solution 1:
Windows 8 (or 10) allows you to add the touch keyboard button to the taskbar. Simply right-click the taskbar and select "Show touch keyboard button". You can then control the keyboard with the mouse, using the same long press as you described for a phone keyboard. This keyboard allows access to Œ through O and Æ through A. It also has additional keyboards of emoji, etc.