When I create metadata for a Nikon .nef raw file, PL5 doesn’t automatically generate an associated xmp file for it. I have to go to “File->Metadata->Write to Image” to create the file. When I copy a Nikon .nef raw file to another computer along with its associated same-named .dop and .xmp files, the metadata does not appear when I reopen the .nef file on the new computer. Furthermore there is no method to direct PL5 to import the contents of the .xmp file to restore the metadata. This is a real problem for me, and I’ve not found a way to deal with it.
PhotoLab does not automatically sync metadata in .xmp sidecars with metadata in its database.
Synchronisation can be switched on in PhotoLab’s preference settings. Note that automatic sync can create problems when other apps are used to edit metadata too: New metadata written by app A can be overwritten by older metadata by app B depending on circumstances.
DPL version 5 writes settings and metadata to .dop and .xmp sidecar files. Metadata can be exchanged between apps through .xmp files, while .dop files store the settings that were applied to a photo, but also metadata.
You have to describe what you are doing more in detail. I think this matter has been discussed earlier in other treads. From what I remembered Nikon cameras are writing the metadata you can add in the camera to the very file itself and into the EXIF elements while Photolab has most of it’s focus on IPTC.
The only metadata that I’ve found recorded in the NEF files from my Nikon D850 is the xmp:rating tag and the usual makernotes stuff.
PL5 reads the rating from the NEF file and writes it to both the DOP file (and the XMP file, either automatically, or when explicitly exported)
You can then alter the rating in PL5 and it will get written to the DOP and the XMP files, but the rating in the NEF file will remain unchanged.
Problems start to occur as soon as you do something like change the rating in the XMP file in some other software. If you do this, PL5 will revert to reading either the DOP file, if one exists, or the NEF file if not.
You can then end up with 3 different ratings: NEF, DOP and XMP.
As @platypus says, the PL5 DAM is not yet reliable enough to attempt to correctly synchronise metadata (including Rating) if you also use another app as well.