After having been using Linux for over 20 years now, one of the few things I really miss in Windows, is the "Compose Key". It does exist, but until today, I was never happy with the mapping. For ages I have this mapped on the Caps Lock key. But under Windows this sometimes leads to a "stuck" caps lock. I've tried different Compose Key applications on Windows, and they all had the same problem.
I was looking for something like .Xmodmap on Windows, and today I found it. You can rebind scan codes using the Windows Registry.
An example entry might be the following:
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout] "Scancode Map"=hex:00,00,00,00,00,00,00,00,02,00,00,00,5c,e0,3a,00,00,00,00,00
This maps scan code 3a 00 (usually sent by the caps-lock key) to 5c e0 (usually sent by the right Windows button). So now pressing caps-lock is interpreted as the right windows key by the OS. This one can be safely bound as compose key as it's not a "sticky" key like caps-lock.