Question: On Topdon Phoenix Smart there was a virtual floating button for screenshot. Where can I find it on Topdon Phoenix Max? I went through the entire menu both in the app and on Android and nothing.

This is the screen shot button on the Phoenix Max.

Tap the second button from the left in the lower-left corner of the main interface — it looks like a photo icon — to take a screenshot.
You can view the captured screenshots in User Info > Photo Album.