Cool, thanks for reporting that. For file transfers any SCSI ID that the device is on will show the same file list: for example, if you've got HD0.img, HD1.img, and a bunch of CD images in a CD3 folder, you can use 0, 1, or 3 as the SCSI ID to see the "shared" folder files. The ID is more important for changing images, in the previous example only ID 3 would work for changing CDs and it would only apply to that emulated CD drive.
Just for background info, at the moment scuzEMU doesn't support scanning for devices, to avoid having to match a specific firmware name or send vendor-specific commands against potentially incompatible devices. It sounds like a future toolbox version might change how this works, so if that happens a "Scan" button might be added.