Right now we only support inline edition for macros declaring a List<Block> content type. It would be really nice to add support for an HTML content type so that we could make the html macro editable inline. I guess it wouldn't be too difficult since the content would be HTML and thus directly editable by CKEditor.
OTOH it would be a great usability improvement for users since right now they have to edit the HTML macro using the standard macro dialog and thus have to know HTML.
See for example https://forum.xwiki.org/t/style-class-attributes-for-list-items-not-a-whole-list/5307/4?u=vmassol for a use case.