For the first hunk, it is using the array key that is assigned to each row in protected function initVideos() (also used for the keys on groups in protected function initGroups()). But yes, it would be possible that when new sections are added, the array key is missed being added and it could be missing.
For the second hunk, the difference is between the array being rendered through Url::fromUri (see below) where we have to declare the attributes to assign the ID that a fragment could scroll to, versus in the first hunk it is being rendered through a table theme function.
$link['url'] = Url::fromUri($link['url']);
I'll be honest, even though this would semantically be correct to add IDs to the group sections that could be scrolled to using a link fragment, it doesn't actually work because the groups are in that scroll box controlled by the search filter input, so the page does not actually scroll down to the targeted group. This is probably just an artifact of how it was originally built, but ideally it would be value that the search box picks up as a default filter value if passed through the URL, but that would be a net-new feature.
Alright, to make it a bit more clear, I just adjusted the summary which would encapsulate the current patch, which overall is "the external library link is broken - the tag is broken, and it points to something that doesn't exist" and this patch fixes both of those. Hopefully that works and is a bit more succinct in describing what is fixed.
I actually wrote one commit for each, but the diff put them in one patch. Should I separate them into two patches?
Added a small patch for fixing the closing tag, and added in unique IDs for the rows generated in the help page (including the missing "libraries" fragment).
kyletaylored → created an issue.