How can I type Greek letters with triple diacritics on macOS?

I can type a single acute accent, such as **ά**, **έ**, **ί**, **ό**, and **ύ**, as well as a diaeresis, like **ϋ** and **ϊ**. However, many Greek words require certain letters to have both an acute accent and a diaeresis, such as **ΐ** and **ΰ**. On Windows and Linux, this can be done by pressing the tonos (΄) twice and then selecting the desired letter. However, on macOS, pressing (΄) a second time cancels the input. How can I type these characters on macOS?