Hooray! Zero to Hero is in Early access now! Ok, back to work making it better...
Zero to Hero is super data-driven. All of the information about the bosses, the levels, the skills, and even the characters comes from little data files shipped with the game. Now you can edit those!
This will still be an involved process with multiple tools. I'm not shipping a tool to unpack the game data, for example. But for someone comfortable with modding games, this should be everything you need: https://github.com/foxor/VBModTools
Let's take a little tour through the serialization format:
Each ".tbes" file, as well as each ScriptableSerailizable asset stored in the unity resources, has a shared format. The first 2 bytes of the file specify the version number, so that I can run data migrations, if we need to reinterpret the file contents in a different way later. Next, 4 bytes describe the length of the file. The length is probably not necessary, since each has it's own file at the moment, but it's "polite" and useful for knowing how big to make the buffer. Then, there's a whole big binary chunk of data describing one object:
Each object is encoded the same way: A header describing the type, and then a big data block. Some data types list the size, but some have fixed size that can be inferred from the type alone. Most objects are lists, so most of the time, the first element is a 4 byte int specifying the number of elements in the list.
If the type was something simple, like SInt. The payload is just the int data.
If there are any sub-objects, they are serialized the same way: type + payload.
There is an editor in that github link that will let you change those files. If you inject your own types into the game assemblies, you'll be able to serialize them the same way.
In fact, that github contains a little mini-game engine for making turn-based strategy games. If you'd like, you can toss away the whole Zero to Hero thing and make your own game. Have fun!