This is a great idea; my go-to approach is the "I'll use PowerPoint to do that and take a screenshot" mindset since I don't have a need for publication quality output.
I really like the comparison site that you have created - it's great for learning these languages. I would love to see a plugin for Obsidian for the times where I need to add a custom drawing to my notes. It looks like there already are plugins for PlantUML[1] and graphviz[2] today.