As you pointed out in the comments, that your difficulty is setting up a structure in TreeView , I'll leave a solution with that focus.

For the solution I used:

• A TMemo as the basis for the file.
• A TTreeView .
• A TValueListEditor to store the fields that will be outside the tree, invisible because it will only serve to store the temporary data.
• Other TMemo to display the fields of the selected node in the tree.

Codes

DeclaretypeTVetorDeString

typeTVetorDeString=arrayofstring;

Clickthe"Process" button

var
   i: Integer;
   Linha: TVetorDeString;
   NohNivel1: TTreeNode;
   NohNivel2: TTreeNode;
begin
   SetLength(Linha, 0);

   for i := 0 to Memo1.Lines.Count-1 do
   begin
      Linha := StringParaVetor(Memo1.Lines[i]);

      NohNivel1 := nil;
      NohNivel2 := nil;

      AddNoh(NohNivel1, nil, Linha[0]);
      AddNoh(NohNivel2, NohNivel1, Linha[1]);

      ValueListEditor1.Strings.Add(Format('%s;%s;1=%s', [Linha[0], Linha[1], Linha[2]]));
      ValueListEditor1.Strings.Add(Format('%s;%s;2=%s', [Linha[0], Linha[1], Linha[3]]));
      ValueListEditor1.Strings.Add(Format('%s;%s;3=%s', [Linha[0], Linha[1], Linha[4]]));
   end;
end;

procedure TForm1.TreeView1Click(Sender: TObject);
begin
   if TreeView1.Selected.Parent = nil then
   begin
      Exit;
   end;

   Memo2.Clear;
   Memo2.Lines.Add(ValueListEditor1.Values[Format('%s;%s;1', [TreeView1.Selected.Parent.Text, TreeView1.Selected.Text])]);
   Memo2.Lines.Add(ValueListEditor1.Values[Format('%s;%s;2', [TreeView1.Selected.Parent.Text, TreeView1.Selected.Text])]);
   Memo2.Lines.Add(ValueListEditor1.Values[Format('%s;%s;3', [TreeView1.Selected.Parent.Text, TreeView1.Selected.Text])]);
end;

Function StringParaVetor

function StringParaVetor(const pString: String; const pDelimitador: Char = ';'): TVetorDeString;
var
   i: Integer;
   aux: string;

  begin
     SetLength(Result, 0);
     aux := EmptyStr;

     for i := 1 to Length(pString) do
     begin
        if pString[i] = pDelimitador then
        begin
           SetLength(Result, Length(Result)+1);
           Result[High(Result)] := aux;
           aux := EmptyStr;
           Continue;
        end;

        aux := aux + pString[i]
     end;

     SetLength(Result, Length(Result)+1);
     Result[High(Result)] := aux;
end;

Procedure AddNoh

   procedure AddNoh(var pNoh: TTreeNode; const pNohPai: TTreeNode; const pTexto: String);
   var
      i: Integer;
   begin
      if pNohPai = nil then
      begin
        for i := 0 to TreeView1.Items.Count-1 do
        begin
           if TreeView1.Items[i].Text = pTexto then
           begin
              pNoh := TreeView1.Items[i];
              Break;
           end;
        end;

        if pNoh = nil then
        begin
           pNoh := TreeView1.Items.Add(pNohPai, pTexto);
        end;
      end
      else
      begin
         pNoh := TreeView1.Items.AddChild(pNohPai, pTexto);
      end;
   end;

Explaining

Button1Click

Go to the StringList line-by-line of the Memo1

for i := 0 to Memo1.Lines.Count-1 do

Each line has been transformed into a vector with the function StringParaVetor :

Position 1 of the vector is a first level node, I add it only if it has not yet been added using the procedure AddNoh :

AddNoh(NohNivel1, nil, Linha[0]);

Position 2 of the vector is a second level node (first level child):

AddNoh(NohNivel2, NohNivel1, Linha[1]);

  ValueListEditor1.Strings.Add(Format('%s;%s;1=%s', [Linha[0], Linha[1], Linha[2]]));
  ValueListEditor1.Strings.Add(Format('%s;%s;2=%s', [Linha[0], Linha[1], Linha[3]]));
  ValueListEditor1.Strings.Add(Format('%s;%s;3=%s', [Linha[0], Linha[1], Linha[4]]));

This part can be optimized with a multi-line loop.

TreeView1Click

To show in Memo2 when clicking on the corresponding node, the idea is to search for the "key" stored in ValueListEditor1, and add the corresponding Value.