Most of the pictures are visible now and they are enough to confirm my previous post.  The "Raiser" is a NVME adapter, called Dell Ultra-Speed Drive.  There are 2 types, duo and quad, you have the duo. Each NVME drive will connect to 4 lanes of PCIe.  You have a duo adapter, in order to support 2 NVME drives, it required the PCIe slot with 8 lanes or more.  On your motherboard, it has 2 PCIe slots, the short (black) one is 4 lanes, the long (blue) one is 16 lanes.  The "Raiser", Dell Ultra-Speed Drive, is currently plug into the x4 slot, and the graphics card is on x16 slot.  You won't be able to utilize another NVME SSD into the "Raiser".  Even if you do, the OS can't see it.
You'll have to excuse me... I'm old! Online Customer Support wasn't able to answer these questions clearly...   [IMAGE]                     1. This console has three SSDs thus far - the first is the boot drive, the second is the 1st storage drive, and the third is the 2nd storage drive. The third SSD (the 2nd storage drive) resides in what I think is called a "riser," which rests in a PCI-e slot. This "riser" (Dell P/N 023PX6) had one more slot available... Would it be no issue at all to just plug in another SSD?   [IMAGE] 2. The package was shipped with two other items - P/N 0CJV5Y (which looks like a short  PS/2 Cable with a "pigtail"), and P/N 06719X (which I think is the Remote Power Switch). I have no idea where to hook these things to. No instructions came with them, and Dell Tech Support has thus far been unable to identify the parts. Any idea where they go?
Dell Precision 3450 SFF SSD "Riser" and Other Parts