I'd like to delete specific messages from a conversation in Messages 7.0.1 – is this possible? The messages in question originated from iPhones where you can tap "Edit" and select individual messages for deletion, which I've done, but I can't find a way to delete them from Messages on my Mac (where they appear because I have iCloud syncing turned on form Messages).
I found out how to do it: single click on the message/picture you want to delete so that it is highlighted. Then, right-click and you will be given the option to "Forward...", "Copy", or "Delete..." the message. Click "Delete...".
Note: Doing so will ONLY delete that message from Messages on your Mac. If you want to delete the same message on any particular iOS device (iPhone, iPod Touch, iPad), you have to delete it on each device individually.
Double click the messages, and tap Delete. You will receive a prompt verifying your desire to delete that message. Accept the prompt, and the message should be gone on your Mac.
In my testing, it looks like you may also have to delete from your syncing iOS device as well. It certainly isn't an instantaneous sync over.