Welcome to the Magix user to user forums, so not a contact for any Magix staff and I suspect very few users of MAC computers actually visit here, sorry.
However, my belief is that you would uninstall the app and its associated FX in exactly the same way as you would uninstall any other program on your computer.
Forgive me for posting in the wrong area. I looked for a link for Magix tech support and this was the closest I found. Do you know how to actually contact Magix themselves? Thank you.
No apology is necessary but does that Apple article not provide the answer to your question?
I am not sure that Magix Support staff will be able to offer any additional guidance but if you want to create a Support Ticket you need to click on the Support link to be found in the header of any forum page and then follow through each succeeding page, always choosing the option to Ask Support or Email Support.
However, there is no option to choose Independence as your software but if you choose "General" on the initial page and then "Show all topics", at the bottom of that page is a link to "Contact Support" and then "Contact Support; Send Email".