I can’t remember where I read this (Martin Fowler maybe?), but I agree that “box and line” diagrams should be enough for most design cases.

I was eager to use UML when it came out but I agree with the article, the only thing I kept was sequence diagrams. Most of the rest of it was just a complicated way to represent stuff that is best represented in code or plain documentation.

I’m also not afraid to use stuff that’s out of fashion. I use simplified ER diagrams, and even flow charts on occasion.

But the tool I use most often in design is SQL DDL…

I have also used Mermaid (using a modified Docsy theme in Hugo) and it is also great. Using Typora to edit Mermaid is also excellent.