I imagine this has been suggested before, but I can't find anything about it in the forums or the issue tracker. I wish that there was a way to preview what is entered in the editor on the same screen as the editor. Currently, using the Atto editor you have some idea of what a quiz question will look like within the editor, but math doesn't render in the editor, for example, and items like drop-down menus and cloze questions don't give you any idea of what they look like within the editor. The only way to see the final result is to finish the question, save and display it, and if changes need to be made, you have to reopen the question for editing. This can be really cumbersome.
I have two big wishes for Moodle's text editing. First, I wish there was a way to preview text without saving and closing the item, dipslaying it, and then reopening the item for editing if there are issues. Second, I wish Markdown was more thoroughly integrated. Using html is way to verbose. Look at stackexchange.com as an example of a Markdown editor that is robust, user-friendly, and provides a real-time preview of the output.