Add pics to LR catalog and have them reside on the laptop drive.
BackUp the pics to the travel drive. Edit the pics as usual.
Open the laptop with travel drive connected.
Open LR catalog on laptop. Select the trip images and move all of them to a folder on the travel drive.
In Lightroom, select all of the trip images in the LR catalog and “Export as a Catalog” to the travel drive.
Shut down Lightroom on the laptop
Move the travel drive to desktop.
Open LR catalog that's on the Desktop Computer (not the newly created one on the laptop).
Import the entire trip catalog from the travel drive.
Select all of the imported images and drag to organisms folder. This could take a while. It moves the images to the iMac database from the travel drive.
WHEN CREATING A NEW FOLDER TO SEND TO ITS URL TO FRIENDS ….
When creating a temporary folder (such as Cover Photos) note that any photos in the new folder will show up in searches as repeats of pics that are already in the catalog.
To avoid this, go to ORGANIZE, select the new gallery, go to SETTINGS>SECURITY AND PRIVACY and set the folder page or gallery to UNLISTED. This will assign a 7 character code to the gallery name. So the gallery URL you send to friends will need to include the 7 character extension.
It may look like this:
Also in the Settings … set the Search By Web to NO, and the Search in Smugmug to NO.