Is there a way of masking code in studio, such as password protection or with user rights?

Such a strange task. If you need to store some sensitive information, do not store it in the code. Store it as settings somewhere, so it will be accessible during runtime with checking rights.

I've seen some places where the ^ROUTINE global is fully or partially deleted after compilation. I suspect that the same would work for ^rMAC or ^oddDEF - you'd have to test it. One company that I'm aware of encrypts the ^ROUTINE global after compilation which has the added "benefit" of making it extra difficult to debug errors! If you really want to hide your code you could compile the code on an identical system and then just deploy the object code.