I haven’t tested what happens when you have had write metadata checked prior to this feature with regards to flag state. I would suggest doing a few small tests with your catalog to see what happens if you make a small edit change to a pre-existing photo that had a pick flag already applied. You’d have to check in either another LrC catalog (where you import that photo to see what metadata comes in) or using Lr desktop’s local feature to see what metadata is displayed. Once you know what happens, and if you decide it is worth updating 100K past images for flag state, I’d do a test on a small subset (5K or something) to see how long that takes, and then go from there.

Thank you, Rob, but this creates even more questions in a way:

1) I have “Write metadata to XMP” on in the Settings – so that answers my first question.

2a) If this functionality is new, it means all the previously written metadata in XMP do not include any flag status (I was aware of that) versus the fact that any new photo of mine now automatically has the flag status in its XMP metadata. So that in turn means we have to manually select all photos made before this version of LrC, go to Grid view and then choose the Metadata > Save metadata to file command in order to update all old XMP files!… With a catalogue of almost 100,000 photos on an external HDD (no SSD) with a rather modest write speed, I think this is going to take an enormous amount of time before the progress is complete!

2b) Am I correct in assuming that, when we edit an “old” photo (flag status not in the metadata of the XMP file), thus forcing old metadata to be overwritten by new metadata, the new metadata will include the flag status?

With the latest update, it is just part of the functionality. You can select photos in Grid view then go to Metadata > Save metadata to file, then let it run until the progress meter completes.

Question #1: How do we turn on this feature or is it simply “included” now in the option to write Metadata to XMP?
Question #2: What about all the previously flagged photos in our libraries? How do we get those flags written to XMP?