The horrors of a graphical programming tool

Recently I had the opportunity to use a graphical programming tool. The problem was to automate an industrial process, and what could be better than a flowchart-like tool? is apparently what the pioneers thought. The tool had been used on several other units, with varying "success". This means I had legacy code to start with. While this certainly does not speak for other tools, and of course the legacy code had a hand in the experience, I want to document here some of the horror-ful experience.