You can put them in the main story summary, which avoids the chapter-spoilers. That's perfectly fine. You could even put them all at the top of the first chapter, if they don't fit in the summary field, which is only 240 characters.
As long as they are somewhere a reader will see them, and know what to expect in the course of the story, we're good. The reasoning is that certain things are triggers, and we don't want readers getting blindsided by running into content they'd not willingly have read.
And in the forum thread, if you wanted to include them in the index, next to each chapter, that's absolutely fine as well. Since readers would find the index url after reading a chapter, it certainly wouldn't be a spoiler for them.