Steps to reproduce:
- create a page with an extension tag for which VisualEditor does not have special logic, and which has some parameter (e.g. <templatestyles src="Foo"></templatestyles> - avoid self-closing syntax which is handled more incorrectly (T177180))
- edit the page in VE
- click on the extension tag (<> icon) then the Edit button
- edit the src field
The "Done" button will not become active - apparently it only listens to changes in the main content, not in the parameters.