Thanks.
Somehow I didn't notice the "Load older files" bent arrow button before

My problem is this: I want to search for posts of a specific poster. So I get only the newest ones. I cannot make the search more specific because there is no way to search for a combination of both a poster and a subject string.
Unless putting the poster into a custom filter - but if it filters the already returned results - it does not help.
And, even if it worked, I may not know the subjects of the poster's older posts.
But with this "Load older files" button, it seems that it is possible to retrieve older posts step-by-step - if the number of those steps is unlimited.
Interesting, if that requires a new search each time or the server keeps all the last search results of each user until the next search.