Ok, after some research my conclusion is:
you can't see side-car files in Lightroom
and also that
Lightroom does not really support a RAW+JPEG workflow
By RAW+JPEG workflow I meant being able to:
(at the user's discretion) Review both files together, while being able to tag both files at once (say, mark both files as Rejected with a single command).
As far as I know, there is currently no way to translate PP3 to XMP sidecars, or vice versa.
And developers are often reluctant to adapt their program to read data written by another program, especially for formats like .PP3, which can change without warning between program versions*.
Even exchanging XMP files from different programs isn't all that evident....
It's a repository of *.dtstyle files, not XMP files... those are generally used for file-specific information. Styles can be managed in the "Styles" panel on the right-hand side in lighttable mode.
No, I don't think that it is supported. I'm not sure though if it is generally possbile.
To find out the truth, we need to look at different Specifications.
(Hint: All Page numbers in the following text are the page numbers a PDF reader reports, not the one on the bottom of the page.)
This documentation states, that Lightroom ...
XMP files do not contain references to the original image file, so in principle, it is possible to use the same XMP file for multiple images with different extensions.
ExifTool does not normally "overwrite" files. When updating a file, it creates new tags and changes preexisting tags, as needed. Preexisting tags in the destination that are not in the source ...
There are several XMP tags that DigiKam writes for ratings, but the most important one will be:
xmp:Rating="0" // values 0 (none) to 5
digiKam:ColorLabel="0" // values 0 (none) to 9.
// xmp:Label is used only if it is a Lightroom-compatible color
Rank=0 // values 0 (none) to 5
ColorLabel=0 // RawTherapee uses only ...
At your step 5., when you export a RAW file from LR to PS (or when you open a RAW file with PS, make some editing and then save it in TIFF format and import it back to LR), a TIFF get created. However, this TIFF has no sidecar file attached, so you won't find any.
So back in LR with a TIFF file, you expect the changes you made to be saved in a XMP file... ...
Actually, none of these answers point directly to a workable solution.
Firstly, ensure that the following preference option is selected :
Edit > Preferences > General > "Treat JPEG files next to RAW files as separate photos"
Now, irrespective of whether you immediately try to search for your JPEGs or after you close and reopen the application to search ...
May I suggest you to use our Daminion as a workaround to transfer your metadata from sidecar xmp files:
1. Import your JPEG files into Daminion.
The program will import your changes from sidecar files (it will check each file and compare modified date of an original JPEG with its sidecar xmp file)
2. Select all the imported files and select Action > Write ...