Adding a column in transaction LX03: I'm trying to add a column in transaction LX03, using the "Column" statement, but without success. What could be the reason?
Transaction LT03 is implemented as an ABAP list screen, not via a table control. You cannot add a column, but here is an alternative solution that will help the user:

Add a toolbar pushbutton "Show xxxx". When the user selects a list row and clicks the button, you display additional information for the selected row.