gridcad
this is a very-much-WIP project to make a gui based graphical digital circuit designer
right now it's linux only and very far from usable but it's a fun project to code on.
git submodule init ; git submodule update ; make
I first got introduced to GUI based circuit design in college (Eindhoven University of Technology) where the local digital design department had created a tool called IDaSS (Integrated Design and Simulation System) (https://www.sciencedirect.com/science/article/abs/pii/0165607490902488) which allowed simultaneous design/simulation. While the big blocks were placed graphically - the detailed logic was coded in a smalltalk dialect.
Recently I saw a set of youtube videos on the subject of digital design that showed a much more fancy looking way of doing the principles of IDaSS. Go check out the channel from Sebastian Lague: https://www.youtube.com/watch?v=HGkuRp5HfH8 He even has code on github as well, unfortunately it seems to be written for a game engine -- not my kettle of fish
Another reference is the Steam game called "Turing Complete" which is a hoot to play and shared also some of the same GUI design ideas.
I'd like to also thank Cody Snider for his cu.pcf file that made the template for the CU fpa board a lot simpler.