Welcome to the forum.
Other programs can be used to do what you want, either from inside PrE, or in a stand-alone.
Now, I do not know what might/might not be available for Mac, and some searching might be required, but users have recommended Phantom Drive, and another utility, with a similar name, that eludes me this AM. Those utilities basically tell PrE that a folder on the HDD is really a BD burner, and then PrE just goes about burning to that, thinking that it is burning to a BD burner. I am sure that something like that exists for the Mac.