HI, User can enable notificaction for collaboration setting, you can also write an workflow extension (see Kristof's extension http://projects.ez.no/createsubtreenotificationruleevent).
"I have a workflow where editor is approving a content added by users (before object is publish). Editor is notifying about a new content to approving. Everything works fine." As you said, so do you mind if you could give me this workflow, I need this for my forum. Thanks