Go to the atto settings page admin/settings.php?section=editorsettingsatto Read the Toolbar config description. Note that in English it says "The list of plugins and the order they are displayed can be configured here. The configuration consists of groups (one per line) followed by the ordered list of plugins for that group. The group is separated from the plugins with an equals sign and the plugins are separated with commas. The group names must be unique and should indicate what the buttons have in common. Button and group names should not be repeated and may only contain alphanumeric characters."