Actually, that is not totally true... One could write a tool that sends windows messages to e-sword that emulates keyboard input.
I have a prototype that works in concept against Pradis (Expositors). Getting access to the controls can be flakey (I suspect timing issues). If I timeout or loop until success it works, but this makes it very slow.
If I ever get it into a usable state, I will make it avaliable to the forum.