To sum it up, you requested :
- Toolbar Search Engine Support : A user kindly provided a tool to do it
- Icon Support Middle Size : Already built-in
- Horizontal Support : no answer provided ... maybe you should link your account to have this kind of request answered
- Menu Button / Label - & Error! : You got the answer why things are working that way and can not be changed (which is by the way quite standard)
- Hide Scrollbar for Custom Menu : You had the answer why things are that way, which once again is pretty standard in Windows world
- Button Right Click Support : we're in it, and had at least a start of way to do what you want.
In about two month, you probably get first rank in asking for new features, had answers to all but one.
Yet, it doesn't seem to be good enough for you as you consider nothing has been done, which is obviously false, and you still consider the program not offering what you want (I wish you good luck on this one, because if you can't customize Opus the way you want, you'll probably spend the rest of your life trying to find another software that does).