That's a good question, but it maybe because at the root of it you have an object/class called check box and its attributes and methods are defined by object. These object are not rendered the same as formatting is by the browser.

So in your example that select box has a list method which doesn't have a property that supports indentation.

You'd have to write a new set of methods that extend the current form inputs. Depending on the browser I guess you could load as an extension or add-in.

Hope that helps.