While in typing mode, I have no easy way to type any words containing vowels with a macron. The special character bar should be an automatic option for any boxes requiring an answer in ʻŌlelo Hawaiʻi. I can copy/paste the ʻokina, but the kahakō is not available.
Are you on a computer or a mobile device?
The web page should detect that you are using a physical keyboard and offer you a string of special characters below the entry box. Are you getting those?
If you are in one of the mobile apps the virtual keyboard will allow you to type the special characters. Touch the letter you want and hold your finger on it until a box pops up with variations of that letter. You can hold on the apostrophe to get the rotated version used for the ‘okina.
I am currently on the web version. The special character string shows up most of the time, but sometimes, as with this question, it is absent. I think it may have something to do with boxes that allow the use of a word bank, which I am opting out of.
I'm in the same situation. The special character string needs to be available.