let
    
.....


#"previous step" = ...

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Create Total row
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TotalRow = Table.Group(#"previous step", {}, {{"Col 1", each "TOTAL"},
                                     {"Col 2", each List.Sum([Col 2])},
                                     {"Col 3", each List.Average([Col 3])}, 
                                     {"Col 4", each List.Sum([Col 4])},
                                     {"Col 5", each List.Sum([Col 5])},
                                     {"Col 6", each List.Average([Col 6])},
                                     {"Col 7", each List.Sum([Col 7])}
                                     }),
    combineTotal = Table.Combine({#"previous step", TotalRow })
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in
    combineTotal 

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Create SubTotal row
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//create subtotals for each region
    group = Table.Group(#"previous step",{"Col 1"},{"temp",each _ 
        & Table.FromRecords({[
            Col 1 = [Col 1]{0} & " Total",
            Col 2 = List.Sum([Col 2]),
            Col 3 = List.Sum([Col 3]),
            Col 4 = List.Sum([Col 4])
        ]})
    }),
    CombineSubtotals = Table.Combine(group[temp]),