Maori language macrons and other accents and symbols can be found in the rich text editor.
If you edit the page and click on the "omega" / (insert symbol) icon Ώ in the rich text editor icons, then in the dropdown field choose the Latin Extended-A option, you will see all the options you can choose to make the letters look as follows:
ā ē ō ū
The following is an image of what you'll see once you've clicked on the Omega / insert symbol icon and selected Latin Extended-A: