It would be useful to have an option to expand the editing panel to either a custom width (via dragging) or a full width view (via a button on the toolbar).

This is particularly useful for when inline editing functionality is disabled for more complex components. It also gives the user an option to choose what editing experience they prefer regardless of the reason. Some editors may prefer to have the full field view instead of seeing the preview take up the majority of the screen, and this preference may change from page to page depending on the content.