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Description
Right now in the dev edition, we are hiding table of contents items beyond the second level. (See also whatwg/wattsi#53 where we contemplate not outputting them at all.)
benschwarz/developers.whatwg.org#59 by @silviapfeiffer indicates that it would be helpful for people to have the table of contents expandable to beyond two levels. This should be relatively easy to do with a little JavaScript.