Thanks SaschaFranck! Heads up, all, there were a couple of alterations I had to make to SaschaFranck's steps to get it to work for me:
NOTE 1: After these steps, eventually had to boot up HELIX normally (w/o holding switches 6 & 12) in order for Line 6 Updater, in offline mode, to find Helix
NOTE 2: I had to 'sign out' of Line 6 Updater in order to get to the sign-in screen with the 'offline' option (sign-out in the ACCOUNT section of the menu-bar)
After following SaschaFranck's steps, my Line 6 Updater program still wouldn't recognize my Helix in "safe boot" mode (many tries with several cables and different USB C ports on my Macbook).
Not sure what kind of "unexplained miracle" occurred through these iterations, but I finally just tried rebooting my Helix normally for the heck of it ... and once again launched Line 6 Updater and selected 'offline' mode. My Helix was recognized like nothing wrong had ever happened and I was finally able continue on to pointing to the Flash Memory file I'd downloaded.
Helix now successfully updated to 3.11