Relevanssi – any way to include pages rather than exclude them?

I’m using the free version of Relevanssi (2.9.12)

I have a site with 400 pages – but I only want to make 20 pages searchable.

Am I right in saying that the only solution is to add the page IDs for 380 pages into Exclude these posts/pages from search:?

It would be much easier if I only had to type in the 20 IDs that I want rather than the 380 I don’t want!

Any ideas, anyone?