Yeah, Sync could be more discoverable. It doesn't seem to be advertised. You can find it via "Menu -> Synchronize" or in settings though as you've noticed.
then there is 'quite complex' process as it requires to add passphrase
That's for extra security. You don't have to do that.
and there is no 'wizard' instead one need to again click somewhere, look for something and so on.
Yeah, it's a little weird that if you remove focus from the Sync toolbar icon dialog while trying to enter your user name and password or when creating a new account in the dialog, it closes where you have to go back and click the icon and start over (click sign in again).
The experience could definitely be better.