Hello Doug,
I have a Pi3 and the easiest way I have found to backup an SD Card is to get your self a memory stick as big or bigger than your sd card and use the Sd Card Copier app on the Pi to back it up. You should find it in the Accessories menu.
When you have a Backup copy on your memstick you can then use ?Balena Etcher on the Mac to clone it to another SD Card.
Note - with a Pi4 from what I understand you can boot off your backup usb memstick and restore back to your Sd Card, (I dont have a Pi4 so not tested).
That is how I worked out how to have a reliable restore solution for my Pi using my Mac.
Since then I have invested in a USB SD Card reader so I can bypass the Mac/Balena Etcher step and do it all on the Pi.
Heres a link to the SD Card reader I bought (uk site so not sure if you can access it?)?
Hope this helps.
David - M1BFP.
David Warren