Yes, currently reports are the only way to sort notes independently of
sources. You should change the preference first, then create the
report--let me know if that doesn't work and I'll give you more
detailed instructions.
From your post on forums it seemed like you could also sort the
sources by date to view your notes, since you have one note per
source, and the date that begins the note is the same as that of the
source--is that not the case?
There is a ticket for allowing for viewing of notes independently from
sources.
https://www.zotero.org/trac/ticket/672
This ticket will get done a lot faster if more people request this
feature on the forums.
Best,
Elena