How to create admin field for a module password

Development
, ,
1

Use obscure as the field type and Magento\Config\Model\Config\Backend\Encrypted as the backend_model:

<field
    id='client_secret'
    translate='label'
    type='obscure'
    sortOrder='3'
    showInDefault='1'
    showInWebsite='1'
    showInStore='1'
>
    <label>Client secret</label>
    <comment><![CDATA[]]></comment>
    <backend_model>Magento\Config\Model\Config\Backend\Encrypted</backend_model>
    <depends><field id='enable'>1</field></depends>
</field>