It's a bit late now, but my solution is to have the images and catalog on the external. If you've done this, just plug in the drive and navigate to the .lrcat folder on the drive-double click it to open in Lightroom.
If you've got a catalog on the laptop that you want on the desktop, or to be added to the desktop catalog, attach the drive to the laptop and run Lightroom. Choose All Photographs in the Catalog panel and then File>Export as Catalog to the drive.
Close Lightroom and move the drive to the desktop. In the desktop catalog, choose Import from Catalog and choose the catalog you put on the external drive.
I tried your suggestion…I think.
When I navigate from my desktop to the connected external hd I see the folder I want. The lrcat folder is down the list a bit and when I double click it it asks if I want to open it in another catalog. It has an older date by it anyway. I must have misunderstood your directions.
When I open LR on my desktop and look in my folders panel at my HD files, the folder I want is not there. My desktop LR does not recognize it I assume because it was created on the laptop LR.
If I choose IMPORT in LR on my desktop and navigate to the folder on my external HD I can see it. But if I import it, I fear that the adjustments made on the road will not come through.
I know there has got to be an easy way to do this!
Actually, let me try your second suggestion. I think it may be the step I missed. Don't worry. Ill get this! Its late.