When nesting, it is helpful to filter on the name of the keyword to nest and the keyword to nest it under. This usually keeps both records in close proximity on the same screen.
When working with keywords, it is very useful to turn on "Show All Keywords Inside Matches." When nesting keywords LR has a habit of refiltering each time a keyword is added, or moved. This becomes very combersome when working with thousands of keywords. To keep the lists more managable, it is helpful to keep keywords collapsed for which one does not need to see its descendants. The re-filtering really causes a lot of busy work after each modification. It often moves the record one is working on out of sight, requiring one to refind it. I see no need to re-filter when adding new keywords, deleting and nesting. It would be very appreciated if this behavior in LR would be changed to only filter on an initial filter query.