Here is a demonstration video that goes through this process (Change column names.mov, right click this link to save the movie to disk for better viewing):
Here is a DeviceEditor .xml saved design file resulting from saving after the demonstration above (Change column names.xml, right click and save link as to save the design file to disk):
Within the design canvas portion of the DeviceEditor display, the name of each of the columns is displayed in the header row above the collection.
Within the "Collection Info" tab in the panel on the right side of the DeviceEditor display, it is possible to change the names of the columns. In the first column ("Column Name") of the collection table, click on desired column entry and edit the column name as you see fit. Generally, column names are useful for combinatorial designs, where the column can be named so as to reflect the class of part variants it contains (e.g. "terminator" might be a good name for a column that contains a variety of terminator sequences). Note that when you click on a column entry within the collection table, the parts contained within the column (along with their "Forced Assembly Strategy", if any) is displayed below the table in the "Column Contents" text box. The assembly orientation of each column is presented in the second column (whose header reads "Direction") of the table. The number of items within each column is presented in the third column (whose header reads "Items in Column") of the table. The Forced Assembly Strategy of each column is presented in the fourth column (whose header reads "FAS") of the table.