Adding a custum column based on an particular cell

[qmhernandez]

Is there a way to add a dynamic custom column that returns the contents of a cell for the entire column? I need the conents of 'First Column' row 1 to become an entire row of duplicates without having to manually type it in as a custom column as I have done in the pictures below.

[KNP · Accepted solution]

This should do the trick.

let
  Source = Table.FromRows(
    Json.Document(
      Binary.Decompress(
        Binary.FromText(
          "i45WCkotSE0sSU1RCEvMKU1VitWJVnLMyy/JSC1CEknML07NK4Ewi/MzUkvywOz81KK8gtIUKLs4I6+ktAjMKU0pSs0H64gFAA==",
          BinaryEncoding.Base64
        ),
        Compression.Deflate
      )
    ),
    let
      _t = ((type nullable text) meta [Serialized.Text = true])
    in
      type table [Column1 = _t]
  ),
  #"Added Custom" = Table.AddColumn(Source, "Custom", each Source{0}[Column1])
in
  #"Added Custom"