type
  TVMOverlay = record
    FileName: string;
    Title: string;
    Start: TSQLTimeStamp;
    Duration: TSQLTimeStamp;
    Kind: TOverlayKind;
    Input: integer;
    OverNo: integer;
    IsOn: boolean;
    RunBySched: boolean;
  end;
  TOverlayList = TList<TVMOverlay>;
...
procedure SaveActionToXmlNode(const aAction: TVMOverlay; var aDoc: IXMLDocument);
var Node, SubNode, Attr: IXMLNode;
    Tmp: TSQLTimeStamp;
    DT: TDateTime;
begin
  Node := aDoc.DocumentElement.AddChild('overlay');
  SubNode := Node.AddChild('filename');
  SubNode.Text := aAction.FileName;
  SubNode := Node.AddChild('title');
  SubNode.Text := aAction.Title;
  SubNode := Node.AddChild('start');
  SubNode.Text := SqlTimeStampToStr('dd.mm.yyyy hh:nn:ss.zzz', aAction.Start);
  SubNode := Node.AddChild('duration');
  Tmp := aAction.Duration;
  Tmp.Year := 2021;
  Tmp.Month := 1;
  Tmp.Day := 1;
  DT := SQLTimeStampToDateTime(Tmp);
  SubNode.Text := FormatDateTime('dd.mm.yyyy hh:nn:ss.zzz', DT);

  Attr := aDoc.CreateNode('kind', ntAttribute);
  Attr.NodeValue := ord(aAction.Kind);
  Node.AttributeNodes.Add(Attr);

  Attr := aDoc.CreateNode('input', ntAttribute);
  Attr.NodeValue := aAction.Input;
  Node.AttributeNodes.Add(Attr);

  Attr := aDoc.CreateNode('overno', ntAttribute);
  Attr.NodeValue := aAction.OverNo;
  Node.AttributeNodes.Add(Attr);
end;


procedure SaveOverlaysToFile(aOverlays: TOverlayList; const aFileName: string);
var XmlDoc: IXMLDocument;
    Root: IXMLNode;
    i: integer;
begin
  XmlDoc := TXMLDocument.Create(nil);
  XMLDoc.Options := XMLDoc.Options + [doNodeAutoIndent];
  XmlDoc.Active := True;
  Root := XmlDoc.CreateElement('overlays', '');
  XmlDoc.DocumentElement := Root;
  for i := 0 to OverlayList.Count - 1 do
  SaveActionToXmlNode(OverlayList.Items[i], XmlDoc);
  XmlDoc.SaveToFile(aFileName);
  XmlDoc := nil;
end;

<overlays>
  <overlay kind="1" input="0" overno="1">
    <filename>D:\photoes\DSCN0875.JPG</filename>
    <title>DSCN0875.JPG</title>
    <start>02.03.2021 18:40:00.000</start>
    <duration>01.01.2021 00:01:00.000</duration>
  </overlay>
  <overlay kind="1" input="0" overno="3">
    <filename>D:\photoes\P_20170922_114554.jpg</filename>
    <title>P_20170922_114554.jpg</title>
    <start>02.03.2021 18:41:00.000</start>
    <duration>01.01.2021 00:01:00.000</duration>
  </overlay>
  <overlay kind="2" input="4" overno="1">
    <filename></filename>
    <title></title>
    <start>06.03.2021 18:38:00.000</start>
    <duration>01.01.2021 00:10:00.000</duration>
  </overlay>
</overlays>