How to group rows dynamically

How about this?

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    DynamicColumns = List.RemoveItems(Table.ColumnNames(Source), {"Name", "Period"}),
    #"Grouped Rows" = Table.Group(Source, {"Name", "Period"},
        List.Transform(DynamicColumns, (col) => {col, each List.Max(Table.Column(_, col)), type text}))
in
    #"Grouped Rows"

This takes the column names other than "Name" and "Period" and maxes over them in a Group By step.