What problem does this feature solve?

You can automatically add some tags to the vue template. Currently, these tags are manually added, but the accuracy and uniqueness cannot be guaranteed manually. In addition, manual addition is trivial, so we hope that we can modify or add corresponding to the Vue AST specification AST, then you can generate new Vue code

What does the proposed API look like?

 const data = ast.createIdentifier("data-sz");
const str = ast.createStringLiteral("123");
 return ast.createAttribute(data, str);

If you are requesting new features, you should go through an RFC, https://github.com/vuejs/rfcs.