ScriptableRendererData uses ScriptableRendererDataEditor with IMGUI. Which makes SaintsEditor unable to kick-in.

To use the functions in SaintsEditor, inherent from SaintsScriptableRendererData

using SaintsField.ScriptableRenderer;

public class MyScriptableRendererData: SaintsScriptableRendererData
{
    // ...
}

Result:

To use URP, inherent from SaintsUniversalRendererData:

using SaintsField.ScriptableRenderer;

public class MyUniversalRendererData : SaintsUniversalRendererData
{
    // ...
}

Note: this requires you to enable SaintsEditor in project too. If you can not, you also need to inherent from SaintsScriptableRendererFeature

using SaintsField.ScriptableRenderer;

public class MyRendererFeature: SaintsScriptableRendererFeature
{
    // ...
}

If you do not want to inherent from SaintsUniversalRendererData at all, please do Tools - Saints Field - Enable SaintsEditor To Scriptable Rendererer