TYPO3 Core

When you modify the CType of a content element, the fields that are no more visible still retain their content;
think of example the switching from "Text" to "Header" : if something is written inside the bodytext, it is preserved, and if you switch back to Text again, the content is there.

This is a suggestion (very poor and early) to add a sort of "migration wizard" that should appear when you change the CType of an element

- the wizard should list the tt_content fields
- the wizard should suggest which content are no more available on the "target" CType (and vice versa)
- the wizard should suggest with a dropdown what to do for each element; the dropdown should have at least two values:
- the same field which means that the field content will be preserved
- empty which means that the field content will be lost

I attach here a couple of visual examples, just to visualize the idea.