The regular MediaWiki source editor allows the user to adjust the size of the edit box by dragging a feature in the lower right. The CodeEditor lacks this feature for its edit box, which is really frustrating when you have considerable screen area to spare and is editing a long source code.
You can, however, adjust the size of the CodeEditor edit box indirectly by first turning off CodeEditor, adjusting the edit box size of the regular editor and then turning CodeEditor back on. This resets your position within the source code, however, and the edit box size is also reset when previewing pages.
So, it would also be nice if the adjusted edit box size did not reset at previewing, as it currently does for the regular source editor.
Furthermore, your position in the CodeEditor edit box resets when you preview pages, unlike the regular editor; it would be nice if the position could remain unchanged for CodeEditor as well.