[columbo]

I think to really get visual coding to work it would need to start from circuit design; Vin, Vout, ICs, logic gates etc.

That doesn't really get you towards end-users writing code but I'd find it pretty useful when trying to look at a complicated process.

[nabla9]

Many circuit design tools have the ability to use either visual circuit diagrams or VHDL. Visual diagrams are useful in many cases, just like UML diagrams, but using only them would be pain in the ass.