Update:

I had to delete and re-install 11.3 (Mac OS 10.15.4) before it finally "saw" the content library in the UI. Weird, because the content library tab was there, but empty and without a way to add any runtimes--no +/- signs in the UI. I then had a way to add my DAZ3D runtime directory, but had to reboot in order to populate my previously saved scene with my DAZ figure (V4.2). Just a little stress - whew!