New documentation standards for form elements are being discussed at #1617948: [policy for now] New standard for documenting form/render elements and properties → . Whereas there is still some debate as to how to document common elements. There has been consensus that code examples and properties specific to the form should be documented with the classes that implement them. This issue serves as a meta-issue to track the work required to move code examples and property documentation into those classes.
Create child issues for each of the "similar" elements (e.g. those that use #options). Create form element documentation for each class containing:
Active
11.0 🔥
documentation
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.
For me, the most important missing documentation is that we need a Drupal 10/11 version of the Drupal 7 "Form API Reference" page. Perhaps this is done as more than one page, but somewhere there needs to be list of valid values for #type and a way to find out what properties can be used with each type.