Soon after starting work on what later became Flow-Based Programming (FBP), I decided that I should leave the block layout entirely up to the application developer... A few years later, James Martin (1981) was working on what he called 4th-generation languages, and the blocks were prone to moving around unpredictably as the text was changed... Very confusing, as people do like things to stay where they are put! This actually fits in with the idea of "loci" alluded to elsewhere in this page. In FBP, "stepwise refinement" is a key part of the design process, so you get a hierarchy of simple structures... I agree that you could add a function to "prettify" your diagram(s), but this should still be under the developer's control. And if you make it simple to move blocks around (as in DrawFBP), it's probably not worth the trouble!