You could certainly edit them directly. However, Simon always recommends
not keeping your yWriter project in Dropbox, because it's known to
produce locking problems with yWriter.
https://sites.google.com/site/ywritersj/faq/ywriter-and-dropbox
Another thing is that you will have difficulty identifying which rtf
file is which on the phone, because they are just given arbitrary
numbers in the order each scene is originally created. You would have to
look inside the yw5 file and read the xml yourself to link them to your
chapters and scenes. Even worse, you would have to write your own
android app to open the yw5 file on the phone at all (as far as I know,
there's no text reader that can attempt to open files with unknown
extensions).
ywSynch gets around both of these problems by letting you keep your
yWriter project out of Dropbox, but get a set of sensibly organised and
named files in the Dropbox. You can tell it to synch them as rtf, in
which case it just copies them between the yWriter project and Dropbox,
and back again (without needing LibreOffice).
Either way, yWriter won't automatically pick up changes made externally,
but when I ran into this problem a while back Simon added a feature to
update the word counts after doing external edits (Tools/Force wordcount).
Trevor Prinn
ywSynch Author