As a SharePoint power user you probably face with a task of advanced field managing in list item forms. You might need to hide or disable a field in a list item form before it is displayed to a user, depending on some condition you define. FormDesigner is a cutting-edge application for SharePoint 2013 which enables you to do so easily!
It’s implemented as an app part that can be added to Display, Edit or New list item form (only ListFormWebPart is supported). The app part has a few of simple properties. Conditions for visibility and availability of fields are defined in a XML settings file which is stored in the settings library of the app.
This is a demo version of the app, it may manage only one field of a list item form (only the first target field in the XML settings file will be processed).
The full version named FormDesigner is also available on the store.
Both versions of the app can be used on Office 365.