Open VCD
From usb_tb, Add usb_dp
From usb_tb, Add usb_dn
Select them both in the wave viewer (starting with usb_dp)
Press F4, enter any name 'USB'
Right click on the new vecot, Data Format / Transaction Filter Process / Enable and Select
Click "Add Trans Filter to List" button
Select the dec_usb.sh script
Once it's in the list, select it and click OK
The Vector should now be 'usb_signalling-1/Bits'.
Right click on vector and select 'Insert Blank'
Repeat the above 2 more times
Then drag & drop those new blanks just under the vector line (rather than under each line representing the individual Dp/Dn lines)