When I started with Anvil I spent the first few days trying to create a tree with dynamic loading. I had in mind ajax, HTML, CSS, and I knew what I wanted. It was a waste of time. Anvil is different.
Then I have created a few apps without trying to break the constraints that Anvil “forces” on you. After another week I was more familiar with Anvil and I was able to nest repeating panels inside repeating panels and my dynamic trees were way more flexible than what I could have done with ajax & co. I did find some limitations during the process, reported and got them fixed, like this one.
As I started getting familiar with what you can do and my company started asking for a custom look, I spent some time in one “Standard Theme” app (with a huge help from the forum) so it would match the company expectations. The app does nothing, it has just a few test forms that show how the various components look
Now when I create a new app, I clone it, replace its theme folder with the one from “Standard Theme” and push it. These are a few quick ugly manual steps, I wish there was a way to define an app theme template rather than using the clone/replace folder/push trick, but it does the job. After this it’s only Python and online IDE (or PyCharm when I work on more complex classes that need more love).