I get the feeling that graphical programming is the tooling problem. The fundamental issue is that diff on textual code has no equivalent in a visual paradigm

I get the feeling that graphical programming is the tooling problem. The fundamental issue is that diff on textual code has no equivalent in a visual paradigm that doesn't have side effects - one example is that color often has meaning in visual systems, and thus is hard to use for showing differences. I'd love to be proven wrong around this though.