How to move a tag from an image file to make a DigiKam tag ?

[plowmail2010 at gmail.com]

Windows 7
DigiKam 8.2.0
SQLite

How do I set a DigiKam tag via an image file using exiftool?

When I set a tag value of "sky" with digiKam, exiftool shows the tag 
value in these fields:

IPTC
   Keywords
   Catalog Sets

XMP
   Categories
   Tags List
   Last Keyword XMP
   Hierarchical Subject
   Subject
   <Categories><Category Assigned="1">Sky</Category></Categories>

When I set those fields in the image file with exiftool, digiKam's 
Metadata display shows those fields, but the tag does not show up on the 
thumbnail display.
Do I have to do something to get a tag from the image file into 
digiKam's database?

Bob