This Power Query function handles headers which have been split onto multiple rows

powerquery-fnCombineHeaders.m

(Source as table, header_condition as function) as any =>
let
    // two row header
    hh = Table.SelectRows(Source, header_condition) ,

    // list of new column headers
    h = List.Accumulate(
        Table.ToColumns(hh),
        {},
        (a,b) => List.Combine({a,{Text.Combine(b," ")}})
    ),

    // get the data records (without the two header rows)
    data = Table.FromRecords(List.Difference(Table.ToRecords(Source),Table.ToRecords(hh))),

    renames = List.Zip({Table.ColumnNames(data),h}),

    // use the new header rows
    tbl = Table.RenameColumns(data, renames),

    result = tbl
in
    result