How to revise keyword list new hierarchy

Question

My present keyword list is just a list of words with no hierarchy. After exporting as a text file, it was noted that many single words have the brackets around them, e.g. [cat] rather than just plain cat.  How did this happen? Can I delete my present list and import a "clean" list? How can I create a hierarchy with my present list?  Reference to a tutorial or manual would be great. Thanks.

Answer 1

If you have a list of words with no hierarchy, such as the one below:
geography
Europe
Italy
Campagnia
Mount Vesuvius
Naples
Pompeii
and if you export the keyword list to a file, and edit the hierarchy as follows:
geography
    Europe
        Italy
            Campagnia
                Mount Vesuvius
                Naples
                Pompeii
everything would be fine if you did not have any photos associated to these keywords to begin with, but if all of the keywords in the flat list of keywords were already associated to photos, then after importing the keyword list, the keywords in Lightroom would appear as follows:
geography
geography
     Europe
         Italy
             Campagnia
                 Mount Vesuvius
                 Naples
                 Pompeii
Europe
Italy
Campagnia
Mount Vesuvius
Naples
Pompeii
That's because Lightroom stores the full path of a keyword hierarchy when that keyword is associated to a photo.
Based on the above hierarchy, the keyword "Pompeii" can be associated to a photo in the following ways:
Pompeii > Campagnia > Italy > Europe > geography
or
Pompeii
So if you already had photos that had the keyword "Pompeii" associated from the flat list of words, this keyword is different from the keyword "Pompeii > Campagnia > Italy > Europe > geography" and there would not be any photos associated to this last one.
All this said, if a hierarchy is to be changed, it is best to do so within Lightroom itself, by drag and drop, and not by doing an export/import of the keyword list.
Also note that when considering keyword hierarchies, it is best to only assign the keyword that is at the bottom of the hiearchy to your photos, as the ones above will automatically be inherited.
As for the brackets around keywords when you export a keyword list, they mean the following:
The square bracket [ ] around a keyword means that the "Include on Export" is not checked in the Keyword Tag options of the keyword; this keyword will not be included in the export of photos that have this keyword associated to them. The other special character used is curly brackets { } which define synonyms of a keyword. A hierarchy is simply defined by adding a tab for each level of the hierarchy.
Here's an example:
[geography]          - this keyword will not be included in exported photos (its purpose is just to organize the hierarchy)
    Europe
        Italy
            Campagnia
                Mount Vesuvius
                Naples
                Pompeii
sport                    - while this keyword is also for organization of the hierarchy,
                              it has more value and I decided that it should export with photos
    running
        3km
        5km
        first race
        half marathon
    soccer
        {football}          - this is a synonym for the word soccer
So the square brackets [ ] have nothing to do with the hierarchy; it simply indicates wether you want that keyword to be exportable or not.
Finally, a good use of the export/import keyword list is to add or remove these brackets, add synonyms to existing keywords, or add new keywords to the hierarchy, but NOT change an existing hierarchy or create one based on existing keywords.
Hope this helps!