Problem/Motivation
During the 2015 usability study, users struggled to visualize how their Field UI configuration choices would appear on the input form of their content type.
Many of them relied on the "default value" widget as a sort of "preview" of how their field would appear on the form. (No doubt many Drupal pros use it for this as well!) It helped them to understand what type of field they were creating, and provided reassurance that they were on the right track during their first attempt at creating fields in Drupal.
If the "preview" didn't show what they expected, they would go back and change some option(s), or delete the field and start over.
Proposed resolution
Provide a live preview within Field UI, (think of the preview available in views). An actual HTML rendering of how the field would appear on the input form, just like the preview of views exposed filters. This would go a long way in helping the user understand the outcome of the various options available as they add fields to their content type.
Not just for noobies
Live previews of field configurations would help prevent mistakes and provide a more efficient and accurate workflow for all users, novice and experienced alike. How many times have you created the wrong field type or settings and not realized it until you saw the form?
(Live previews could also be added to "Manage form display", "Manage display", and "Edit" screens in content type administration, but these should probably be separate issues).
User interface changes
Include a live-rendered HTML preview of the field within the Add field dialog. Extra points if it updates in real time as the user changes options within the Add field dialog (before they click Save to submit the form).
API changes
None.
Data model changes
None.