If you want to help out with the project, I recommend you first read all the current documentation to get an overview of how the API and GUI work. Also see if you can complete the Getting Started tutorial.
After that, here is a list of things you could work on:
- Rewrite the multi-line textbox control
- Rewrite the image viewer
- Making a modern dark-mode visual style
- ... And possibly more things
If any of those sound interesting, please visit #essence on the Handmade Network Discord where I can give more information. Furthermore, if you have any feedback on the documentation, please talk to me about it there as well.