In theory it should be relatively easy to add an option in the Scout extension to select which attributes to search. Meilisearch at least supports selecting search attributes.
If you only want to make titles searchable, then it would be even easier since you could just remove the code that indexes the post content. The same could technically be done for native Flarum search but the SQL request to modify is a bit more complex. In both cases if post content search is removed it would actually be beneficial to rewrite the entire SQL query (or in Scout, the index merge algorithm) to simplify and speed it up since there would no longer be the requirement to search data from 2 different tables/indexes.
With or without Scout, there's a lot that could be done and probably isn't too complicated. But it requires writing a custom extension.
