When developing page resources, sometimes, you just need to write, preview, rewrite, ...etc.
The current choices at the bottom of the page resource are Save and Return, and Save and Display. There is no button just labelled Save. Since Save and Display won't run an external macros (like links to MathJax), you can't preview TeX formatted math with that display. "Save and return" means that you need to return to the main page and in order to return to editing, you must find the small gear icon after scrolling back down to the point in the class that has the assignment.
With modern, multi-tab browsers, its time for just a save button. Then someone in the process of editing and testing would just need to save then then switch to the tab already displaying the page and hit F5.