After a chat with someone at Adobe, I installed the latest build (a very recent one he told me). It miraculously started working properly & saving the check mark for sub folders. In fact it was already checked when I tried an import.
It must have been a glitch in the previous download update which didn't allow LR to save the import setting. I have a rather slow DSL line here & given the time it takes to DL this program, I'm not surprised there was a minor glitch.

Thanks everyone for all the suggestions.

I have one and it can be a lot of fun to use, but I generally save it for those times where its convenience outweighs my need for the better quality results. Let's face it, it a superzoom, although probably the best one in it class. That means there are all sorts of limitations from 18 to 400 millimeters with regard to sharpness at the center and at the edges, distortion, chromatic aberration, speed of acquiring focus, low light hunting, etc. Distortion is fairly well controlled for a lens of this type and it is reasonably sharp at the center but somewhat less sharp at the edges. It is also reasonably sharp through most of the zoom range but less sharp as you approach 400mm. It is not as sharp anywhere in its range as my sharpest Canon and Sigma lenses.

Depending on the integration of your particular copy with your camera body, you may or may not, decide you need the Tap-in to tweak sharpness. Using the Tap-in, which is similar to Sigma's USB dock, takes a lot of time, effort and attention to detail and I doubt most potential owners of this type of lens would be willing, or patient enough, to go through the process successfully.

Whether you will be happy with the 18-400mm depends on your expectations for such a lens and your experience with better, shorter zoom range, lenses. Those who are the happiest with this lens seem to have somewhat different expectations from an optic than I have, and may be less critical of it shortfalls. However, although it doesn't have stellar performance in any particular area, the zoom range of this relatively light and compact lens is extraordinary. It is a very convenient all-in-one lens that meets the needs of a large number of people. if your expectations are more forgiving than mine, the 18-400mm Tamron might well be the only outdoor lens you will ever need.

You can set up your folders just like you could in Win7.
It's not intuitive because it is unfamiliar - this goes away after awhile.
It's smaller on your drive than Win7
You have all the tools you had in Win7 to modify, edit, make notes, access, look up stuff, download pictures and etc (copy/paste, drag/drop, etc)
Win 10, at least the Pro version, is more secure.
You can use it EXACTLY the way you use Win7.

I have and use both and don't understand your objection other than having a problem with change in general.