There is currently no report function which allows a person to report multiple related offending posts in one fell swoop.
This has 2 current workarounds:
1) report 1-2 of the offending posts and try to explain that there are other such posts in the thread, risking losing context and scale of the moderation request
2) report each and every offending post - which is feasible if the number of posts that are problematic is low, but if there, say for example 10 posts in the same thread made at different intervals by a person, then the user of the report function runs into the problems where he/she is gated by the 30 second window in between reports, and past that, risk looking "spammy" as the user has just sent 10 identical reports in a very compressed period of time.
A multi-report function would allow the user to choose multiple posts to report at once, ridding of the "spammy" and "gated" component of the single report system, just like a multi-quote function allows a poster to quote multiple people and posts at once without having to manually single-quote each person and copy pasting to a bigger post.