Create a new keyword in the keywords panel: “kplaces”
Drag and drop the other keywords into "kplaces"
Repeat this for several keywords, creating master keywords with sub keywords
In the keywords panel, click the right arrow near “kplaces” or other master keyword
Some of the master keywords shows results in the grid panel, some of them doesn’t but curiously still can be found by filtering (cmd-f)
Some keywords can’t be deleted
If you purge unused keywords, a lot of keywords already assigned are erased without warning
I have installed the operating system from scratch.
I have created a new catalog, and imported the pictures deleting the old keywords assigned during the import
Due to the Lightroom errors, I have reinstalled 3 times.
The only extra action that I have made is to create app keyboard shortcuts in the System Preferences of the operating system, to sort by rating, aspect ratio, etc.