Well, If you have proof that it is supported by the OS, then there will be a way.... but not necessarily an easy one.
You may have to do it from scratch for each OS, find the documentation of the OS (or Toolkit, like GTK), find out what API to call, maybe translate the c headers to pascal, and then call those functions.
Anyway, there is a MouseAndKeyInput package. It allows you to simulate mouse move, and key clicks. I have never tested it, and I do not know if it supports simulation across applications, yet it might...
If so, you may be able to send keystrokes...
But as I said, I never used it myself.