I recently flagged a few porn uploads and since those videos violated the rules they've been removed. How can I flag a YouTube playlist instead of having to click on each video?
On a playlist page, you can click on the vertical three dots button (More) to flag the playlist. Note that this only flags the playlist itself, not the videos within the playlist.
If you often flag videos, you may want to apply to the heroes program as it offers scaled flagging tools: https://support.google.com/youtube/answer/7124236?hl=en