Dynamic reordering of columns

Here are examples of how you can dynamically set the column order.  If you can provide an example/screenshots of what the size column names are and the outcome you are trying to achieve I can provide a more specific solution. 

Match the column order for a different table:

Table.SelectColumns ( #"Name of Previous Step", Table.ColumnNames ( #"Other Table Name" ) )

Columns without "Size" in the name followed by columns with "Size" in the name:

Table.SelectColumns ( #"Name of Previous Step", let
   varBufferedList = List.Buffer ( Table.ColumnNames ( #"Name of Previous Step" ) ),
   varColumnsWithoutSize = List.Select ( varBufferedList, each not Text.Contains ( _, "Size" ) ),
   varColumnsWithSize = List.Select ( varBufferedList, each Text.Contains ( _, "Size" ) ),
   varFinalColumns = List.Combine ( {varColumnsWithoutSize, varColumnsWithSize} ) in
varFinalColumns )