There is currently no option to maximize the columns size. It become difficult to see data in small sized box. There should be option to maximize every row/column in a DataTable.
We shipped use experience improvements for working with DataTables that include a larger input field when editing values. Should you need to work with a large DataTable with variables that have very long string values, we recommend using a spreadsheet to manage the values and then just copying and pasting them within the DataTable.