My main catalog is on my desktop CPU at home. This is where I upload all of my projects. I have a rather large project that I want to edit down on my laptop while I'm on vacation and then update or replace or whatever the same group of photos on my desktop when I get home. What is a logical step-by-step way to do this? I appreciate any suggestions, links or opinions.
You can Export As a Catalog the files you want (you only need Smart Previews unless you want to 'Edit in Photoshop', etc), there is a choice to include Negative Files if you want files..
Then Import from Catalog back into your main catalog, computer.
As Geoff said, use the Export Catalog option. I would first set up a Collection of all the images you want to take with you, then right or control click on the Collection and choose, Export this Collection as a Catalog. Include the negative files to have full editing capabilities.
Copy the newly exported catalog folder to your laptop. Then import the lrcat file back into the main catalog when you return.