Vincent, No this is something you will have to modify the AttributeTableOptionsMenu.mxml file from the API to remove. So here are the steps involved.
- Copy the AttributeTableOptionsMenu.mxml from arcgis_api_for_flex_3_5\ArcGIS_Flex\src\com\esri\ags\skins\supportClasses in the Flex API download to src\com\esri\ags\skins\supportClasses in your viewer project. Notice this is not the same as the src\com\esri\viewer\skins folder.
- Copy the contents of the arcgis_api_for_flex_3_5\ArcGIS_Flex\src\assets\skins folder to src/assets/skins
- In that file comment out the exportGroup HGroup.
- Re-compile the viewer