As noted above, "My next challenge was to get the Fling FTP to work with multiple Google accounts."
Problem finally solved. The trick was wading thru Google's obtuse instructions for adding a Google account to the Google Drive For Desktop software. The trick is, the "Add another account" MUST be done by Right Clicking on the the little taskbar Google Icon (NOT while using your browser). The Browser has another "Add another account" feature which allows you to define UN/PW for several Google accounts to aid in online browser access to the added Google account list. However, using the taskbar icon to "Add Another Account" actually creates an additional drive on your PC. That is, you'll then have the added drive when clicking on the "This PC" (or in file explorer) where you see all your normal drives (e.g. C:, D:, USB, CD, etc.). When you first install Google Drive for Desktop it create a G:drive which is the first account you specified when setting up that software. But, using the little taskbar icon to "Add another account" it actually creates another drive letter (e.g. I:drive or J:drive in my case) which which you can then access when setting up a destination for an NCH Fling routine. Bingo. You can create added Fling routines to map from any of your traditional drive folders to any of the other Google Drives. And, as always, any Fling routine can be set to Manual or Automatic as you wish.
I added a short cut on my desktop to each of their respective Google drives. This so I could quickly see what's in them without having to use my browser to log into and view their drives. Heck, I can even then do copy/paste etc. from anywhere to Paste to any of the Google drives or their folders.
WHEW!