When I select a number of documents in the binder, rather than have the inspector change to Bookmarks I’d like to have keywords panel that lets me know which keywords are applied, similar to how Photos does it – with shared keywords in black, and keywords not applied to all selected documents in grey.
If view documents in outline view, can have column display keywords as written or color chips and thus becomes easy to see files/folders without keywords.
The inspector moves to the bookmarks panel only if your multi-selection is displayed in outliner or corkboard view. (It does however display the metadata panel and keywords once you select a single document inside those views.)
Viewing those documents as a Scrivening does allow you to see the keywords. But only one document at a time. (So it ain’t that different than the two other view modes.)
The only way I can think of to get close to what you ask, is, like @GoalieDad said, through the outliner. But you don’t get any indicator as to what keywords your documents might have in common; although sorting your documents by keywords seems to get almost to that.
Displaying keywords by color is also achievable in corkboard view, but with no real benefits in this case.
P.S. I only noticed the “wish list” tag after posting my reply.