No re-importing!! This never helps and often makes things worse.
You upgrade the Lightroom 4 or 5 catalog to Lightroom 6.
Open Lightroom 6. If there is not a prompt to upgrade your previous catalog, use File->Open Catalog, point to the Lightroo 4 or 5 catalog file.
I should have been clearer. I did successfully updated to LR6. The catalog was brought in and everything was good.
Only recently did I think of re-doing these bracketed photos. I got reading about Aurora HDR and thought that LR would be easier and just as good or probably better.
I have all the original RAW files.
So then I don't understand the original question. You have all the photos now in Lightroom 6?
Yes but not all of them. The originals were in LR5 and then I updated to LR6 with the LR5 catalog. For example - three photos 001.NEF / 002.NEF / 003.NEF - could not be bothered to use Photomatix so I processed only 002.NEF and did not use 001 or 003. I suppose I could re-import 001 & 003 reset 002 and then HDR merge. I was just thinking it might be easier to use a new catalog but I'm not sure how. Difficult to explain.
Why are you even thinking about re-importing if the photos are in the new Lightroom 6 catalog?
To use the HDR merge function with the unused 001 & 003 shots. That's why I did the bracketing in the first place. It seems a big waste if I don't use them. It was the time wasting of Photomatix that caused me to quit using the other bracketed photos. The LR HDR merge was not available at the time of the original import.
Okay, there's some information missing here.
I do not know what you mean by "unused".
Are 001 and 003 in the Lightroom 6 catalog, or not?
001 & 003 are NOT in LR catalog.
Then they must be imported.
I think everything will be easier in one catalog.
Ok. Thanks. I still think there might be a better way.