I think for the feature request part it would make sense to broaden the request so that this function would be applicable not only to keywords but to any property, as some might call them topics or issues, or something else. So basically, you could have a tab overview for any frontmatter key, like it exists for tags. I think this feature request goes in a similar direction: Show existing values in Properties view.
However, I think this is not a solution for your current issue, as I guess you need a solution as fast as possible.
I don’t know if there might be a plugin that already offers what you want.
As a workaround, Bases or Dataview are great for filtering your notes by specific keywords. Do they have any limitations that make them not fit your approach?