Many years ago I wrote a windows application that could be used to build biochemical models visually. Origially called JDesigner but subsequently renamed to PathwayDesigner. Over the years the code grew larger and somewhat unwieldy. In addition it couldn't run on the Mac. I have decided therefore to rewrite it using more modern tech so that is can run on the Mac as well as Windows. Initially it won't include simulation capabilities since simulators are dime a dozen. It also won't support SBGN or the SBML layout/render standard since htey are hard to support. The GitHub repo can be found here, currenlty at version 0.1.1 https://github.com/hsauro/PathwayDesigner