LabVIEW doesn't restrict SCPI commands in any way. SCPI is a command set that describes the strings that your instrument understands.
Your best bet is to use an instrument driver. This abstracts the communication strings away and instead provides you with an action-based API. For example, an instrument driver may have a method for ConfigureWaveform. This method will then write the appropriate set of SCPI strings to configure the instrument.
Keithley has an instrument driver for the Keithley 6485 at:
http://www.keithley.com/storefront/ps.catalog:downloaditemlist?mn=6485&itemType=Software%20Drivers&template=DocumentTemplate&idetail=keithleyitemdetail&ilistdownloaditemlist&itemListDisplay=download_item_list_view
Good luck.