Rename Nested Tables Based on Condition

Hi JNB3 

You need to use Table.TransformColumns to apply the same transformation to each nested table within the Custom column.

On way to do this, is to first create a function that is similar to your RenamedColumns step (I called this RenameFunction), then apply this function using Table.TransformColumns in the ApplyRenameFunction step below.

let

  // Define a function that will be applied to each nested table
  RenameFunction = each Table.TransformColumnNames(
    _,
    each
      if Text.Contains(_, "back", Comparer.OrdinalIgnoreCase) then
        Text.Replace(_, _, "Back")
      else
        _
  ),
  // Source table
  Source = #"Added Custom",
  // Apply the function to each nested table in the Custom column
  ApplyRenameFunction = Table.TransformColumns(Source, {{"Custom", RenameFunction}})
in
  ApplyRenameFunction

Does this work for you?

Regards