Answer is no as the PCI slot the WWAN uses is only for a wireless controller card. If the board doesn’t have a dedicated M.2 storage slot, then the board has no storage controller on PCIe bus and thus wont recognize an M.2 SSD.
This guy (poster “Ydnaroo” ) got it to work easily (WWAN slot for a SATA M.2 drive), but it’s not the same motherboard (tho’ very similar in age and, visually, in apparent design.)
That’s what gave me the idea...
Well, the M’board has a PCIe storage controller running the existing NVMe drive... But, this may be a question of the BIOS telling the controller that WWAN slot (physically a M.2 SATA style slot can actually function as a M.2 SATA slot? Again, it worked for one poster with a same (or very close) vintage motherboard that (visually) appears to have the exact same slots....
I can confirm that adding a 512GB M.2 SATA SSD in the WWAN slot DOES work in my Dell 5490 laptop. (With my motherboard and BIOS, so, older machines may be iffy.)
Noteworthy is that the new SSD did not immediately show up as a drive in File Explorer, etc.: but it did show up with the mfgr. part number in Device Manager. Then going from there into “Properties” and “Disk Management” I had to initialize the new drive & give it a volume label. That done, it then showed up in File Explorer and I was able to save a couple image files to it, close everything, and then open those files successfully. Copying a few text files from the NVMe boot drive in the M.2 “drive” slot to the SATA drive in the WWAN slot works smoothly too.
Woohoo!