Create new rows that show difference between 2 rows that match criteria

Try this in blank query.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45Wci4tLsnPTS1SMFTSUXIEYufSoqLUvBIgyxSIQZQBhAYiSxgzVgeLzoCi1LLM/NJiuHKYTkuECag6jTDsBCJDU4Rq/NowLAQiYwPc+owxrDM3MMBiGS59SPbBNVpgmoCh1wnDi0AM8oQxbn0m2IIGDZkbgB2AXSO2wEHVaYmmExTuzth0WlpaQhgmyBEZCwA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Customer Name" = _t, #"Part of Business" = _t, #"Current?" = _t, #"NOT DUE" = _t, #"0-30" = _t, #"31-60" = _t, #"61-90" = _t, #"91-120" = _t, #"121-180" = _t, #"181-364" = _t, #"365+" = _t]),
    Cols = Table.ColumnNames(Source),
    RedCols = List.Skip(Cols,3),
    Type = Table.TransformColumnTypes(Source, List.Transform(RedCols, each {_, Int64.Type})),
    ReplacedNulls = Table.ReplaceValue(Type,null,0,Replacer.ReplaceValue,RedCols),
    Group = Table.Group(ReplacedNulls, {"Customer Name", "Part of Business"}, {{"Gr", each Table.SelectColumns( _, List.Skip(Cols,2)), type table }}),
    Trans1 = Table.AddColumn(Group, "Custom", each Table.Transpose([Gr])),
    AddedC = Table.AddColumn(Trans1, "Custom.1", each if List.Count(Table.ColumnNames([Custom])) = 1 then 
Table.PromoteHeaders(Table.AddColumn([Custom],"Column2", each
if [Column1] = "Previous" then "Current" 
else if [Column1] = "Current" then "Previous" else 0))
else Table.PromoteHeaders([Custom])),
    AddedT = Table.AddColumn(AddedC, "Custom.2", each Table.DemoteHeaders(Table.AddColumn([Custom.1],"Total", each [Current]-[Previous]))),
    Trans2 = Table.AddColumn(AddedT, "Custom.3", each Table.Sort(Table.Transpose([Custom.2]),{"Column1", Order.Ascending})),
    Removed = Table.SelectColumns(Trans2,{"Customer Name", "Part of Business", "Custom.3"}),
    Expanded = Table.ExpandTableColumn(Removed, "Custom.3", Table.ColumnNames(Removed[Custom.3]{0})),
    FINAL = Table.RenameColumns(Expanded, List.Zip({Table.ColumnNames(Expanded),Cols}))
in
    FINAL

try this