If you want an integrated solution and avoid multiple external tools (like Visio, PowerPoint, etc.) to create diagrams, here is a very helpful extension.

This unofficial extension integrates Draw.io (also known as diagrams.net) into VS Code.

To create a new diagram, just create an empty *.drawio, *.drawio.svg, or *.drawio.png file and open it.

You should use .svg whenever possible. It's very practical when you make updates without re-importing everything — just make the change and that's all.

Download is available here: Draw.io Integration – Visual Studio Marketplace

Here is the demo:

Draw.io VS Code extension demo