May I sync a Collection with Ligthroom on mac, on ipad and then on a PC Win? If I activate the sync on the third one I got all sync pict removed

Question

I sync a Collection on my Mac with Lightroom
Then I open lightroom on my iPad and I can see and work on it
Then I activate syncing on a pc win, but I got a Warning about syncing catalogue and if I go on, I got the collection synced lost.
thanks

Answer 1

It's clunky, but if two catalogs refer to the same images, you can pass some settings back and forwards between these two catalogs via external metadata on the file. These images may be literally shared, or else separately stored but with changes physically transferred (replicated / synced). But LR Mobile is AFAICT no help at all in this.
Collection membership cannot be replicated this way - to do that directly, you would instead need some method based on passing Catalog data back and forth, as mentioned in another reply. However, as a workaround, if you were to apply a characteristic keyword, you could make a Smart Collection in each place which was based on the presence of that keyword. This alters the problem, into getting the same keyword loaded into images within each of two Catalogs - and that CAN be done via external metadata. However, AFAIK via this workaround, this grouping of the images will not then show up in LR Mobile in the same way, in the form of a standard Collection. However, the keyword should be visible to LR Mobile in due course.
Caveat: besides being clunky, the above's a little hazardous too:
Whenever you write metadata to file, LR goes ahead and unselectively obliterates everything that was previously there in the file. It won't warn you, if this operation overwrites older edits onto newer ones.
Whenever you read metadata from file, LR goes ahead and unselectively updates all that image's settings in the active Catalog. Again, it won't warn you, if this operation overwrites older edits onto newer ones.