How did you collapse text in the comment?! Witchcraft!! I need to know!
First you need to enable Markdown. Go to Settings > Profile, down at the bottom of the Content section enable “Prefer Markdown input where available.”
Once that setting takes effect, you will see the Markdown logo (M with arrow pointing down next to it) in the upper right corner of input box. With markdown, you can also use a limited set of HTML tags. The collapsing content is wrapped in details tag, and a summary tag inside that is the visible part. I’ll try to put example below with extra spaces, maybe it won’t format it?
< details > < summary > Text that always shows </ summary > Content that is hidden unless expanded. </ details >