The description for this plugin says “searchable” but it means the search tool within the table, not searchable within the site I guess.
Correct. If you want to make the content “searchable” in the same way you can search post content, you’ll need a plugin capable of searching this plugin’s cache. I don’t know of one off-hand, but Search Everything might be a place to start.
I don’t know much about those plugins but if there are integration options available amongst them, it might be useful to add some knowledge of this plugin’s caches to that plugin. I don’t think I’ll get around to investigating that anytime this year, however, as there just aren’t enough people materially supporting me for this plugin’s development efforts given the crushing oppression of capitalism to make that a reasonable investment of my time. I would very happily accept patches from others for whom this was a desired feature, though.