TextKit Best Practices (WWDC 2018) mentions the 2010 session, but I cannot find it on Apple's website. Help?

There are references in more recent WWDC sessions, but it's no longer on Apple's website. Help!

The documentation for TextKit 2 is a bit thin. I have a few questions about that: Is more complete documentation available to Developer Program members? When can developers expect for the API documentation to be updated? When will overview documentation, like TextKit 1 has, be available?

I want to add characters to the display of my paragraphs without modifying the underlying text storage. To be concrete, let's say that I want to prefix each paragraph with "Whereas, ". Further, when I drag out a text selection on a paragraph that's displayed this way, I do not want "Whereas, " to receive a selection highlight. Using TextKit 2, it's pretty easy to accomplish the first part using a NSTextContentStorageDelegate whose method textContentStorage(_: NSTextContentStorage, textParagraphWith: NSRange) -> NSTextParagraph? adds my prefix to each paragraph. I modified the WWDC21 demo program to do it. I appreciate how I can avoid glyph munging by using TextKit 2 instead of TextKit 1, it will save a lot of trouble. If I drag a selection across the prefix, then it receives the selection highlight. What's more, when I drag a selection across the end of the paragraph, the last eight characters (and, I presume, the invisible newline) do not receive the selection highlight. So adding the prefix has skewed the selection indices. It seems to me that the TextKit 2 designers may intend for me to use a NSTextLocation subclass consisting of a "storage" index and a "display" sub-index. On the storage indices there are the characters of the text storage, and at (storage index, display sub-index)-pairs are the characters of my prefix. While the user drags out a selection, I should subtract from the NSTextSelection any NSTextRanges belonging to non-storage text such as my prefix. Am I on the right track, so far?