In Forms 9.1 if I create a new form from scratch and click on a custom HTML I can see that actual code I've added. If I export/import that form or upgrade it (example here) I can't see the custom code.
The code is there, and I can see the result of the code if any (such as a button) but I can't actually see the underlying code. This makes things really complicated if the code I've added is something like:
<div id="signature"></div>
where is won't actually show up in the editor. In fact the only way I can even see if is by previewing and then inspecting the code manually that way.