Recently, I’ve been digging into Monitoring in Azure.
I was really pleased to find that a visual representation of an Azure VNET can be produced from inside the Azure Portal.
Here’s an example

It’s an SVG image.
You can import these into your documentation.
If you select a VNET in the Azure Portal and then locate the “Monitoring” section, you’ll see a menu item called “Diagram”

Just select it and you end up with a downloadable image like above
Have a great day
cheers
Marty