TYPO3 9.5.7 / Extbase：在flexform中添加向导

I'm trying to add the 'add wizard' in my flexform of my extension, but the add button doesn't show up. The flexform itself is working by the way. I want to give the backend users the possibility to add new items from the plugin configuration. ps: Reinstalled the extension, cleared all the caches... My flexform:

<T3DataStructure>
<sheets>
    <sDEF>
        <ROOT>
            <TCEforms>
                <sheetTitle>Viewer Configuration</sheetTitle>
            </TCEforms>
            <type>array</type>
            <el>
                <settings.viewer>
                    <TCEforms>
                        <label>Viewer select</label>
                        <config>
                            <type>select</type>
                            <renderType>selectSingle</renderType>
                            <size>1</size>
                            <minitems>0</minitems>
                            <maxitems>1</maxitems>
                            <foreign_table>tx_myext_domain_model_viewer</foreign_table>
                            <foreign_table_where>AND tx_myext_domain_model_viewer.deleted = 0 AND tx_myext_domain_model_viewer.hidden = 0 AND tx_myext_domain_model_viewer.pid = ###CURRENT_PID### ORDER BY tx_myext_domain_model_viewer.name</foreign_table_where>
                            <wizards>
                                <add>
                                    <type>script</type>
                                    <title>Create</title>
                                    <icon>EXT:backend/Resources/Public/Images/FormFieldWizard/wizard_add.gif</icon>
                                    <params>
                                        <table>tx_myext_domain_model_viewer</table>
                                        <setValue>set</setValue>
                                        <pid>###CURRENT_PID###</pid>
                                    </params>
                                    <module>
                                        <name>wizard_add</name>
                                    </module>
                                </add>
                            </wizards>
                        </config>
                    </TCEforms>
                </settings.viewer>
            </el>
        </ROOT>
    </sDEF>
</sheets>
</T3DataStructure>