I had to give up this nice input method when I totally rewrote WaveLab to make it work for the Mac (WaveLab 7). I did not had time to port this slider stuff. Since then, it has somewhat fallen into oblivion. It is certain that, all these years, I could have done something, but at the same time, I believe you are the only person to have made this remark in almost 20 years. Therefore, it is not necessarily crucial.