To edit draw.io diagrams in VS Code install the extension
Draw.io Integration hediet.vscode-drawio
Alternatively use the web application at https://app.diagrams.net/
Video tutorials and other guides for draw.io can be found here
https://drawio-app.com/tutorials/
An overview of the most important diagrams used in the visual modelling of computing programs by Donald Bell.
https://developer.ibm.com/technologies/web-development/series/uml-basics/