I have my catalog with smart previews on an SSD drive. My pictures reside on a second external drive. I can then make
picture adjustments both on LR Mobile or on my laptop with only the SSD drive attached.
I also have metadata written to XMP files on the pictures external drive.
Here's the question. When I edit photos on the laptop with the external picture drive detached, will the XMP files get automatically
updated when I subsequently start LR with the external drive attached?
No, you would have to run the command after attaching the second drive containing the originals.