You can integrate SaintsEditor with other editors.

public class MyEditorCore: SaintsEditorCore
{
    public MyEditorCore(UnityEditor.Editor editor, bool editorShowMonoScript) : base(editor, editorShowMonoScript)
    {
    }

    public override IEnumerable<IReadOnlyList<AbsRenderer>> MakeRenderer(SerializedObject so, SaintsFieldWithInfo fieldWithInfo)
    {
        if(fieldWithInfo.FieldInfo?.Name == "...")  // skip a field
        {
            return Array.Empty<IReadOnlyList<AbsRenderer>>();
        }
        if(fieldWithInfo.PlayaAttributes?.Any(each => each is ShowInInspectorAttribute || each is ButtonAttribute))  // render ShowInInspector/Button
        {
            return base.MakeRenderer(so, fieldWithInfo);
        }
        // Otherwise, do not render it
        return Array.Empty<IReadOnlyList<AbsRenderer>>();
    }
}

Then, in your editor script:

[CustomEditor(typeof(MyTargetType), true)]
public class IntegerateSaintsEditor: MyEditor
{
    public override VisualElement CreateInspectorGUI()
    {
        VisualElement root = new VisualElement();
        root.Bind(serializedObject);

        root.Add(base.CreateInspectorGUI());  // Fill with default behavior
        root.Add(new MyEditorCore(this).CreateInspectorGUI());  // Fill with SaintsEditor
        return root;
    }
}