@Bruno, still looking for a concrete use case. You can already create a custom type and expose that to BPs, and scan for all instance of that type (or just use a FGameplayTag/FGameplayTagContainer property and scan for people who implement something in a namespaced tag region). Tagging specific properties with metadata is a bit more special case, and the specific kind of metadata (UMetaData) we’re talking about is editor only which further limits the utility.
Cheers,
Michael Noland