I just noticed now that I am using the synchronize tool, that the copy dialog comes up but has no "unattended" mode like the normal drag and drop copy command does. Is there a way to enable the unattended mode in the synchronize tool? If not I'd like to request it as a feature request. 
Only for normal copy/move, I think.
We don't have an "unattended delete" mode, which is something Sync would need.
(When using the Recycle Bin, it's difficult to do as the API doesn't really support it, although there are clunky ways to do it.)
Thanks for the reply. If it's too difficult to do it's fine that it's not implemented, but I figured I'd mention it because it would have been nice to have last night. 
I was only really looking for it because I was trying to copy some files from a dying HDD and it kept like disconnecting itself when it hit some of the bad blocks. I was mainly using the sync tool as a way to see what got copied over and what was remaining/unrecoverable. It would have been nice to have that box with the list of files that didn't make it over instead of waiting on it to pop up each time. But it's not a feature I would be using often so it isn't really a big deal for me.
I understand why it isn't supported for "unattended delete" but it would definitely be helpful for when the "Delete files from destination that don't exist in the source" is unchecked. I could have used this feature right now.
Thanks!
Maybe the Copy Files > Update All or Update Existing commands would work better for you, depending on what you're doing.
Those won't give you a list of things that will be synced which you can look at and turn things on and off before syncing. They'll start copying immediately. But you'll be able to use unattended mode.