The widget API is extensive, but it has it's limitations. Below are some of the more frequently asked questions:
It's currently not possible to update the fields of a form with the updateSettings command. See also this post on the community
You'd expect this code to work, but it doesn't.
You can not hide fields in the widget via the API code. You can hide them via Conditional Fields in forms though.
You can't add buttons or links to other tools and channels to the widget interface.
The widget will not display the following fields: