Hi Avon72,
Thank you for posting your question in this community. From your description, I understand that you would like to edit your presentation slide while in presenting view on Mac as you can do in Windows by switching the windows to hide the presentation view. However, it may not be available on Mac at this moment I am afraid.
In this scenario, I suggest you can raise this idea on PowerPoint for Mac UserVoice or vote on this similar idea about Update a presentation while presenting. It is a channel for Office users to submit their suggestions or feedback and let the product team aware them. Thank you for your understanding.
If you would like to display or highlight the contents to your audiences in slides during the presentation view, you can try the pen and laser tools to achieve it.
For your information:
Turn your mouse into a laser pointer
Best regards,
Dihao