For developers it is not possible to edit the html of a fragment. In ACS this was possible via Edit - HTML.
Once you have created the fragment via the Designer, if the code is not working as it should, you should be able to edit the html as well. That is how developers usually work.
The feature should work something like in ACS where you can add the edit HTML option somewhere.
Current behavior is create a new fragment, but that is not ideal.
