There are at least two different ways to discover the keywords you have created over the years. Most people who use keywords don't remember all of them, this discussion might help if you want to join it. The two ways return two sets of keywords. They may overlap. Keywords are definitely optional for Smart Keywords, and I haven't worked through how the lists overlap. Searches using arbitrary elements found using one method don't yield results searching the other method. But vice-versa there may be overlap. There's more to it of course and these descriptions could use some polish.
If anyone wants to discuss any of those vague descriptions, to flesh it out, I'll be more precise and will try to demonstrate how to recreate.
If anyone wants to criticize that I didn't write a couple of pages and a TL:DR, fine, my goal is discussion and after you get it off your chest ask a question.
If you don't know what keyword and Smart Keywords are, ask.