Connect to the part with the debugger by going to Run -> Connect to -> Silicon Labs ARM Part.
In the memory view, select "Flash:Main Block" (highlighted in green), then "Export" (highlighted in red).
Select format as "Srecord", select start address and length (consult the part's reference manual for this information). Select the file name (use the extension .srec) and click "OK".
In order to use this file with Simplicity Commander, you will need to use a text editor to add the line "S0030000FC" to the top of the file. This image can now be flashed to other parts (or back to the same part) using Simplicity Commander.