Thanks very much for your time and effort and your very prompt reply. I have long appreciated your well-informed comments here on UHH.
I have gone through he steps you recommend. Making the virtual copy before sending image to LR seems to be the key.
What does not seem to work for me, though, is sending the new PSD back to PS and finding there in the history the changes I previously made in PS. It would be nice to be able to revert to the history that was created in PS directly after sending image to PS in the first instance.
If it is not possible to go back to the edits first made in PS, then that is the way it is.
But the idea of a virtual copy does most of what I wanted to do. Thanks again.

I can't speak for everyone ... my own thoughts are that each person should evaluate and understand every step and every action in their back-up strategy. Their back-up strategy is related, but distinct, from their editing process.

One area to consider is how many times are your backing up the exact same file? Once? Twice? Three? More?

Consider Card-A with IMG_0001.raw. If I copy from the camera to my c: drive and import into LR, I still have just this one version of IMG_0001.raw. Assume I format the card in the camera and now the file on disk is the only version. Here's where your back-up strategy comes into play. Do I already automatically back-up the files on C: where I've just copied IMG_0001.raw? If yes, my work and worries are done here regarding IMG_0001.raw as my automated tool sees a new file and creates a back-up, say to the cloud.

Consider instead that I copy IMG_0001.raw from the camera to the C: drive where I plan to edit and at the same time, I copy IMG_0001.raw onto a G: drive that is a back-up. And, I have process (manual or auto) where I back-up both these C: and G: drives. Now I have four copies of IMG_0001.raw. For what purpose?

Consider further in this second scenario that I get IMG_0001.raw into LR and eventually decide IMG_0003.raw is the 'keeper' from a string of images and I delete IMG_0001.raw. Do I also go out and delete the three back-up copies of this image that when the master copy was deleted from LR?

The context of your comment is different from the context of non-destructive PP. People who do image editing use a non-destructive workflow to be able to reverse part or all of the edits to an image. In a raw converter it is not necessary to do this, since the original image is never touched - only the metadata is edited - and the process keeps a baseline of the settings for how the file emerged from the camera. In Photoshop, extensive use of layers and smart objects and the tools to manage them allow one to construct a non-destructive EDITING workflow with full reversibility. Of course no one would suggest that saving a backup copy of any image is bad practice. But this has nothing to do with a non-destructive workflow, and all to do with good data retention practice. Really two different things. Your suggestion is valid for all files, a non-destructive workflow, in this context, applies to image and video editing.

TRAVLR38, you didn't use <Quote Reply>, so we're all left to wonder to which of several comments your question is directed. I didn't recommend a virtual copy as that would seem superfluous, but maybe there was another comment that better explained the idea and this comment was directed.

Regarding not having your layer history inside the PSD, you might need to double-check your PS settings / defaults when you save your changes into the PSD. Assure that you are saving the layers. I only have PSE so it may be different in the main product, but in PSE there's a check-box when you save the PSD indicating whether to include the layers, something you need to select to maintain the layer information.

The context of your comment is different from the context of non-destructive PP. People who do image editing use a non-destructive workflow to be able to reverse part or all of the edits to an image. In a raw converter it is not necessary to do this, since the original image is never touched - only the metadata is edited - and the process keeps a baseline of the settings for how the file emerged from the camera. In Photoshop, extensive use of layers and smart objects and the tools to manage them allow one to construct a non-destructive EDITING workflow with full reversibility.