Also, PlantUML + C4 is like peanut butter & jelly:
https://github.com/plantuml-stdlib/C4-PlantUML
I'll gladly give up control of layout, and accept some ugliness, to never again have to worry about dragging boxes and arrows to be pixel-aligned, and then do it all over again when I add another box...
It looks like Mermaid has C4 support too:
https://mermaid.js.org/syntax/c4.html