There's so much interesting prior work!
I really enjoyed this paper “A Taxonomy of Simulation Software: A work in progress” from Learning Technology Review by Kurt Schmucker at Apple. It covered many of my favorite systems.
http://donhopkins.com/home/documents/taxonomy.pdf
It reminds me of the much more modern an comprehensive "Gadget Background Survey" that Chaim Gingold did at HARC, which includes Alan Kay's favorites, Rockey’s Boots and Robot Odyssey, and Chaim's amazing SimCity Reverse Diagrams and lots of great stuff I’d never seen before:
http://chaim.io/download/Gingold%20(2017)%20Gadget%20(1)%20S...
I've also been greatly inspired by the systems described in the classic books “Visual Programming” by Nan C Shu, and “Watch What I Do: Programming by Demonstration” edited by Alan Cypher.
https://archive.org/details/visualprogrammin00shu_2pf
https://archive.org/details/watchwhatido00alle
Brad Myers wrote several articles in that book about his work on PERIDOT and GARNET, and he also developed C32:
C32: CMU's Clever and Compelling Contribution to Computer Science in CommonLisp which is Customizable and Characterized by a Complete Coverage of Code and Contains a Cornucopia of Creative Constructs, because it Can Create Complex, Correct Constraints that are Constructed Clearly and Concretely, and Communicated using Columns of Cells, that are Constantly Calculated so they Change Continuously, and Cancel Confusion
http://www.cs.cmu.edu/~bam/acronyms.html
Also, here's an interesting paper about Fabrik:
https://donhopkins.com/home/Fabrik%20PE%20paper.pdf
Danny Ingalls, one of the developers of Fabrik at Apple, explains:
"Probably the biggest difference between Fabrik and other wiring languages was that it obeyed modular time. There were no loops, only blocks in which time was instant, although a block might ’tick’ many times in its enclosing context. This meant that it was real data flow and could be compiled to normal languages like Smalltalk (and Pascal for Apple at the time). Although it also behaved bidirectionally (e.g. temp converter), a bidirectional diagram was really only a shorthand for two diagrams with different sources (this extended to multidirectionality as well)"