Table scan and joining data in a sigle value

You want to use the Group By feature, but you have to do the Text.Combine part manually. See the code below:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjDUByIjAyNjJR0lZ58gIOkIxAGleSWliTmZKYkpSrE6OJWFJBalJuJTEJRaUpRYnK/gmpValJyZnJmPqdg3yN2XGFuR1OGwFkkFkn2xAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Fecha = _t, Alumno = _t, Materia = _t, Comentario = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Fecha", type date}}),
    #"Grouped Rows" = 
        Table.Group(
            #"Changed Type", 
            {"Fecha", "Alumno", "Materia"}, 
            {
                {"Comments", each Text.Combine(_[Comentario], ", "), type table [Fecha=nullable date, Alumno=nullable text, Materia=nullable text, Comments=nullable text]
                }
            }
        )
in
    #"Grouped Rows"

Source table:

Final table:

How to use M code provided in a blank query:
1) In Power Query, select New Source, then Blank Query
2) On the Home ribbon, select "Advanced Editor" button
3) Remove everything you see, then paste the M code I've given you in that box.
4) Press Done
5) See this article if you need help using this M code in your model.

Thank you very much for your support.

I have implemented the code, except that when trying to use the grouping result column, in the Report view, Visualizations panel, Table object, the grouped text column is not displayed, is there a way to make the grouping results permanent to be able to use them in the table visual? Greetings.