Very interesting, that if you are not using SPLIT command, just 'Nominal W x H Size' - it still shows you 'x'
If you just need leaf width, why not to extract parameter directly from door object in schedule?
Now how to do it. You need to extract variable that called 'gs_leaf_panel_witdth'. By default this parameter is hidden. So, you need to open a door as Library Part and click on the red cross next to this variable. Then save a door with new name into Embedded Library (after everything is completed, you can delete this file).
After in Schedule Scheme settings dialog you need to click on the arrow next to the button "Fields" and choose "Library Part Parameters". In new window that shows list of available libraries you need to find your temporary door and search for 'gs_leaf_panel_width' and click on 'Add' button.
Now ArchiCAD can extract this parameter from each door (because they are using the same variables names).
After new schedule is set - you can delete the door from Embedded library.
