This will be a new feature in 2.5. You will be able to add (microflow) buttons IN the control bar, instead of having to make a new table column everytime you want custom buttons.
You can't add custom buttons to the control bar (edit: as Robert said, in 2.5 this will become possible), however you can add buttons to a table cell in the lowest row of the dataview. If the buttons really must be on the same row, you could disable the control bar and add your own save/cancel buttons and the rest of your custom buttons next to it.