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The only slight glitch I noticed in my latest test is that synonyms in PM are not recognised as such and are added into the LR keyword hierarchy as if they were keywords in their own right. This is a relatively minor issue compared to the loss of the keywords I was previously experiencing, and maybe there will be a solution to this as well if I continue looking.
Having checked each setting, I had checked "When updating XMP, add Structured keywords to hierarchical keywords field only". I unchecked this, and now keywords seem to be added correctly and are recognised by LR within its keyword heirarchy.
I have an analog problem with CaptureOne and PM.I put hierarchical keywords a|b|c in C1 for RAW pictures, and export a jpg (without XMP),PM find in JPG. a|b|c, a|b, a,b,c I want only a|b|cWhich is wrong, C1 or PM, a solution ?