Unpivot (Append?) Repeating column formats

Hi pistachio  

sorry, just read your second comment previously. you can try the following technique, less "intelligent" action required:

let
    Source = Web.Page(Web.Contents("https://community.powerbi.com/t5/Desktop/Unpivot-Append-Repeating-column-formats/m-p/964070/highlight/false#M462025")),
    Data0 = Source{0}[Data],
    #"Promoted Headers" = Table.PromoteHeaders(Data0, [PromoteAllScalars=true]),
    #"Changed Type" = Table.TransformColumnTypes(#"Promoted Headers",{{"ID", Int64.Type}, {"Datetime", type datetime}, {"Value", Int64.Type}, {"", type text}, {"ID_1", Int64.Type}, {"Datetime_2", type datetime}, {"Value_3", type number}, {"_4", type text}, {"ID_5", Int64.Type}, {"Datetime_6", type datetime}, {"Value_7", type number}, {"_8", type text}, {"ID_9", Int64.Type}, {"Datetime_10", type datetime}, {"Value_11", type number}}),
    Custom1 = Table.ToColumns(#"Changed Type"),
    #"Converted to Table" = Table.FromList(Custom1, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    #"Added Index" = Table.AddIndexColumn(#"Converted to Table", "Index", 0, 1),
    #"Integer-Divided Column" = Table.TransformColumns(#"Added Index", {{"Index", each Number.IntegerDivide(_, 4), Int64.Type}}),
    #"Grouped Rows" = Table.Group(#"Integer-Divided Column", {"Index"}, {{"Partition", each Table.FromColumns(_[Column1]), type table [Column1=list, Index=number]}}, GroupKind.Local),
    Custom2 = Table.Combine(#"Grouped Rows"[Partition])
in
    Custom2

For performance it is crucial to use the "GroupKind.Local" in step "Grouped Rows"

Please let me know about the performance difference to the first Pivot-solution, thanks.

Please not that for this solution it is crucial that you always have the same number of columns per repetition!!