Append Dynamically

1. Split the list of column names into pairs using List.Split.
2. Combine all the number columns by taking the values from the first column name in each pair.
3. Combine all the text columns by taking the values from the second column name in each pair.
4. Combine these two lists into a single table using Table.FromColumns.

Here's a full sample query you can paste into the Advanced Editor:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlTSUUoEYhMgTgZicyBOU4rViVYyArKSgNgUiFOA2AKI08EyxlC1ZkCcCsSWQJyhFBsLAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t, Column2 = _t, Column3 = _t, Column4 = _t, Column5 = _t, Column6 = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Column1", Int64.Type}, {"Column2", type text}, {"Column3", Int64.Type}, {"Column4", type text}, {"Column5", Int64.Type}, {"Column6", type text}}),
    ColPairs = List.Split(Table.ColumnNames(#"Changed Type"), 2),
    NumberCol = List.Combine(List.Transform(List.Transform(ColPairs, each _{0}), each Table.Column(#"Changed Type", _))),
    TextCol = List.Combine(List.Transform(List.Transform(ColPairs, each _{1}), each Table.Column(#"Changed Type", _))),
    Combined = Table.FromColumns({NumberCol, TextCol}, {"Number", "Text"})
in
    Combined