Those hierarchical tags are actually automatically applied by PhotoStructure based on metadata your phone or camera stores. If you add keywords, like "first st

Those hierarchical tags are actually automatically applied by PhotoStructure based on metadata your phone or camera stores. If you add keywords, like "first step" to a photo (by using the Windows file information dialog, for example), PhotoStructure would add "Keywords/first step" to that asset. Most keywords I've seen in the wild are just a word or words, much like a hashtag, separated by comma or semicolon. There are hierarchical metadata fields, but they seem to be used only by professional media services, not consumer applications.