This is not an easy solution, then...i see.

The final suggestion on your link is what I was thinking of too.

Back up the back up. I guess the expansion drive is the way to go. Hubby has one and we tested it out on this laptop. I moved one large file and it was pretty easy. We then deleted it.
It is a bit faster and easier than a back up with included software.

But it seems to me to be just a fancy flash drive? It doesn't have its own power source.

I read the reviews on Amazon for Seagate expansion drives.
Seems the 4TB has many failures.... about 15% were unhappy with it. The 1 TBs were more 5 star.

Kevin suggested Western Digital, so I'll check those tomorrow. I have 2 huge binders with slide and photo envelops (archival) with my old photos of my art work, from the 70's and 80's. I can barely lift them. I made them 2 winters ago. They are about 3 in thick!

But my photos from 2006 til now, are MANY and large pixels... and I use many of them for ideas for drawings. They are about 55 gig.

Kevin has warned me not to leave photos on my camera,or on flash drives for any length of time. He says they are not stable. I looked on Consumer Reports that we subscribe to and it said the same. "do not use flash drives for long term storage".

I'll let you know what transpires.