SUMMARY
It seems there is no way to have the tag tree view (Captions->Tags) use its ‘check’ or ‘…’ display per node to define application state of children nodes to selected image(s).

STEPS TO REPRODUCE
Create a tag structure like:
#Sports
   #Football
       #Player Name
            Name1
            Name2
            Etc
        #Teams
        #Player Number

From a group of images in an album, select 1 image so it is active as a tag target. Apply tag ‘Name1’ to image. 


OBSERVED RESULT
Within the #Player Name parent tag, you will see Name1 show a checkmark if you select only the image selected when Name1 was applied. If you select multiple images, you will see ‘…’ next to Name1 to indicate it is applied to a subset of the selection. The parent tag #Player Name will not change state under these conditions- it will remain unchecked, even if the #Player Name branch is collapsed. Likewise with its parents (#Football, and #Sports).

EXPECTED RESULT
As with the ‘Show Item Count’ option, it would be helpful if the tag indication extended to parents. ‘Show Item Count’ only shows the total number of tags in the branch(es), but it doesn’t indicate if any are active for the selected images (or to any images).


SOFTWARE/OS VERSIONS
Windows: 
macOS: 
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: 
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION

The lack of this indication makes it difficult to determine if one or more images is missing a tag. In some tag classes (i.e. #Photo Attributes) there may not always need to be an active tag for an image. For others, depending on the nature of the content, there is typically going to be several that are 'required' for whatever tag standard the user has created. 

Its not as simple as auto-tagging on import, since often tags cannot be aligned by folder name. In the example above, I could assign the NameX tag, but not the Teams or Player Number tag, etc. If files are copied in externally, or merged there are going to be instances where required tags arent assigned. If you have a #Player Name tag list that has 1000 members, I cannot just leave that branch expanded and look for Name. Even if the image has a Player Name tag assigned, I will not see a ‘…’ at the #Player Name node when I select said image- so I have to physically scroll.