Are you planning to add an example for the template callback?

Would you like to suggest one? I don’t have a use case in mind.

Common use cases would be horizontal alignment, <fieldset>, <detail>, etc.. I have a few older examples of varying complexity for native inputs in https://observablehq.com/d/852ff200776cb9f4 Do you want to limit the example to Inputs widgets, or are you open to including native inputs (minus native button, checkbox, radio)?

https://observablehq.com/@ambassadors/whats-that-noise now uses Inputs.form() with custom template callbacks.

It would be great to add some documentation here, or on the Synchronized Inputs page, about how to bind (or otherwise manipulate) a field on a form. It wasn't clear how to do so at first. For example, https://observablehq.com/d/dca8540d04be23c8 (admittedly, I skipped most of the docs like views which later helped me figure it out)

Not out of the box. You might find this helper useful: https://observablehq.com/@mootari/inputs-submit