If it were to be made so F1 brings up normal reference, and something else brings up library references there should also be a button to switch between the two.
I've explained this already, but:
The point is to allow for better integration of libraries. You can already make a help file for a library that is a webpage users can access, but that's not integrated with DM. People already know to press F1 in DM to get help, there's no reason not to leverage that. If users have to press, for example, ctrl+F1 to get help on library topics, they might as well press alt+tab to switch to a web browser window that contains the library's online documentation.
I'm not sure why people would want it to be a separate tab. Are you afraid that the list would become cluttered? The library's reference pages would only be added to the reference if the library is included in the project. There are about 550 DM reference pages to begin with and most libraries would have just a few reference pages.
I agree with this one 100%.
Either another tab, or an 'included library' reference.
If it were to be made so F1 brings up normal reference, and something else brings up library references there should also be a button to switch between the two.