Here is a demonstration video that goes through this process (Change column SBOL Visual icons.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 SBOL Visual icons.xml, right click and save link as to save the design file to disk):
Initial SBOL Visual icon selection:
Each column within the collection may be optionally associated with a SBOL Visual icon in the header row immediately above the collection. To initially select a SBOL Visual icon for a column, click on the corresponding pencil button in the header row. Doing so will pop-up a new "Change Icon" dialog box, where you can click on the icon you would like to associate with the column. When the cursor hovers over one of the SBOL Visual icons, the description (e.g. "Origin of Replication") of the icon pops up (a handy reference in case some of the symbols are unfamiliar to you).
Changing a SBOL Visual icon:
After a SBOL Visual icon has been associated with a column, it is possible to change the SBOL Visual icon part by clicking on the corresponding pencil button in the header row. Doing so will pop-up a new "Change Icon" dialog box, where you can click on the icon you would like to associate with the column.