using only UI
let
Source = Table.TransformColumnTypes( Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMtQ11zUyMLRU0lEyNAYSxgYgFpqgiSmQAEuYKsXGAgA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [BEG_DATE = _t, START_HR = _t, START_MIN = _t, END_DATE = _t, END_HR = _t, END_MIN = _t, HRS = _t, MINS = _t]),{{"BEG_DATE", type date}, {"END_DATE", type date}, {"START_HR", type number}, {"START_MIN", type number}, {"END_HR", type number}, {"END_MIN", type number}, {"HRS", type number}, {"MINS", type number}}),
#"Rimosse colonne" = Table.RemoveColumns(Source,{"HRS", "MINS"}),
#"Merge di colonne" = Table.CombineColumns(Table.TransformColumnTypes(#"Rimosse colonne", {{"START_HR", type text}, {"START_MIN", type text}}, "it-IT"),{"START_HR", "START_MIN"},Combiner.CombineTextByDelimiter(":", QuoteStyle.None),"ST"),
#"Merge di colonne1" = Table.CombineColumns(Table.TransformColumnTypes(#"Merge di colonne", {{"END_HR", type text}, {"END_MIN", type text}}, "it-IT"),{"END_HR", "END_MIN"},Combiner.CombineTextByDelimiter(":", QuoteStyle.None),"ET"),
#"Merge di colonne2" = Table.CombineColumns(Table.TransformColumnTypes(#"Merge di colonne1", {{"BEG_DATE", type text}}, "it-IT"),{"BEG_DATE", "ST"},Combiner.CombineTextByDelimiter(" ", QuoteStyle.None),"start time"),
#"Merge di colonne3" = Table.CombineColumns(Table.TransformColumnTypes(#"Merge di colonne2", {{"END_DATE", type text}}, "it-IT"),{"END_DATE", "ET"},Combiner.CombineTextByDelimiter(" ", QuoteStyle.None),"end time"),
#"Modificato tipo" = Table.TransformColumnTypes(#"Merge di colonne3",{{"start time", type datetime}, {"end time", type datetime}}),
#"Aggiunta colonna personalizzata" = Table.AddColumn(#"Modificato tipo", "dur", each [end time]-[start time])
in
#“Aggiunta colonna personalizzata”