Moving Collections to a NEW Catalog

Agree with @john beardsworth 

One catalog is a much better approach, avoids confusion as he said. Use keywords rather than a new catalog to allow you to identify the "portfolio-potential" photos.

Related, you could mistakenly choose to do something in the "wrong" catalog, it would be hard to tell the two catalogs apart visually. I have set up my web browser on my home computer in one color scheme and when I work from home, I use the same physical screen, but my work web browser is a different color scheme, idea is to make it easy to tell them apart. And it doesn't help. Mistakes happen. I use the wrong web browser. I know that for most e-mails I recieve, I should not click on "Reply All", but sometimes I do. Again, people make these types of mistakes, especially if you are in a rush or distracted.

You've not missed anything, but be careful before trying to work with more than one catalogue - you can easily waste time and cause confusion. Here for example I'd ask why not just create a portfolio collection?

If you do want a portfolio catalogue, you can use the good old File > Export as Catalog. So select the images, choose File > Export as Catalog, tell it to use only the selection, do not include negatives (ie originals), and go ahead. This creates a new catalogue with all the collections and keywords and other metadata associated with those photos. No new folders are created - the catalogue is pointing to the same pictures as the other catalogue. Now those photos are being managed by two catalogues, a recipe for confusion?

It would be great to move Collections over to another catalog (and not folders associated).

My goal was to move all my portfolio-potential images (in collections) over to its own Catalog.  I only see my file folders available to move. I would imagine LR could find a way for this to work. They have made so many leaps and advances, lately. 

If I am mistaken and it is possible, please share. Maybe I missed something.