I also wanted to begin a similar topic.
SynthMaker is a wonderful program, as there are no other, but -on my opinion- it is not yet mature. (see Ideas and Requests section)
I'm not a big expert here (away from me), but it is known that such graphics processing is very CPU consumption.
In such cases be recourse to hardware acceleration (etc., etc).
Updates are quite rare, and from here assume that the development team is too small.
I now only this much...