[Example Request]: Extend an existing shape/tool with a new property and edit that property
### What's the example?

Hey! I am very glad this exists and I thank you all for creating it :)

At first it seemed easy, but once I started looking deep into what it actually takes to create a shape, it is daunting! So hats off ahah

But so my example request is: how to extend an existing shape (for example Geo/rectangle) with a new property (let's give an example: drop shadow), and then how to edit it in the shape-aware menu (top right). I don't see any examples explaining this, but I might be missing them completely!

Thank you so much for your time.

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct