Dynamically expanding all columns with lists

Have worked out a way!

The step that does it is below. 'GetRecordFields' is a list of all distinct columns in every row of records (this varies by row and is expanded in the first step). I have also nested an if statement to check if the cell is a list because otherwise it produces an error for non list values.

List.Transform(GetRecordFields, each { _ , each if Value.Is(_, type list) = true then Text.Combine( _ , ",") else _}))

Full code is below, which also has steps to dynamically change type to text and remove errors which is required for a data flow. The code in the link that jennratten provided is much more complex but the below should work if you don't have to flatten the json struture.

let
  Source = Json.Document(#"Parameter (3)", 65001),
  Navigation = Source[elementVOList],
  #"Converted to table" = Table.FromList(Navigation, Splitter.SplitByNothing(), null, null, ExtraValues.Error), 
  GetRecordFields = let
    #"Added Record Fields" = Table.AddColumn(#"Converted to table", "ColumnNames", each Record.FieldNames([Column1])),
    #"Select ColNames" = Table.SelectColumns(#"Added Record Fields", {"ColumnNames"}),
    #"Expanded ColNames" = Table.ExpandListColumn(#"Select ColNames", "ColumnNames"),
    #"Removed Duplicates" = Table.Distinct(#"Expanded ColNames"),
    ColNames = #"Removed Duplicates"[ColumnNames]
  in
    ColNames,
  #"Expanded Column1" = Table.ExpandRecordColumn(#"Converted to table", "Column1", GetRecordFields, GetRecordFields),
  #"Expanded lists" = Table.TransformColumns(#"Expanded Column1", List.Transform(GetRecordFields, each { _ , each if Value.Is(_, type list) = true then Text.Combine( _ , ",") else _})),
  #"Replaced errors" = Table.ReplaceErrorValues(#"Expanded lists", List.Transform(GetRecordFields, each {_, 0})),
  #"Changed Type" = Table.TransformColumnTypes(#"Replaced errors", List.Transform(GetRecordFields, each {_, type text}))  
in
  #"Changed Type"