In the meantime, you can unpin the site from the taskbar, remove it from the edge://apps page, and then re-pin the site.
On the touch keyboard you can press and hold on a vowel to access the diacritic forms. To type macrons over vowels, press the grave key (`) at the top left corner of your keyboard, and then press the vowel key for the vowel you would like to enter with the macron ( `+ a = ā, ` + e = ē, etc.). You can add this keyboard in Settings > Time & Language > Language and add the NZ Aotearoa keyboard under the options for English (New Zealand). This keyboard has diacritics needed for typing Māori.
Areas of the OS that use the Segoe MDL2 assets such as the Start menu and Settings app will include the new icon designs which have a more rounded and simplified look and feel. This build includes a new font Segoe Fluent Icons.