Yes Play mode isn’t yet included in the v4 manual, it will be reinstated as soon as possible but that won’t be for a little while. I wrote up a little overview of the manual update for v4 here:
In terms of hierarchical organization – have you got some examples that stand out in particular? In the PDF, the continuous stream of pages doesn’t highlight the structure as well as perhaps the list of contents does in the webhelp version. But depending on your browser, you should be able to see a TOC on the left of the PDF.
For example, each mode has its own separate chapter that covers the key bits of UI in that mode and then sections of things that you can (generally) only do in that mode.
Then there are other sections, primarily the Notation reference at the end which has a separate chapter for each type of notation, where you’ll find information specifically relating to that notation. Another good chapter is Page formatting, that initially goes through the different steps most commonly needed for part & score preparation, with more detailed information and further details in sub-chapters at the end of the chapter.
Finally, on the webhelp simply searching relevant words and phrases should bring up fairly good results. In addition to the body text and index etc, the webhelp benefits from additional keywords that I’ve added based on how users have asked questions in the past.