Hello! Remember that you can contact me directly using the Support form:
https://itch.io/blog/694860/undermax-support-page
Based on your question:
It is simply an iframe with the correct size that I have linked to my github pages where I have the code that allows me to edit whatever I want. You can also directly from itchio, but the problem is that they have to activate the CSS for your page, and you are limited to 5000 characters, which is very little. So this way, I have almost complete control of the Itchio page and I can do nice things.