attach file not showing shared devices

When using Mac Mail however, the attach button (paperclip icon) does not display "Shared" in the left sidebar menu. Please advise how I may attach a file from a Shared device (a PC on the network) to my Mac Mail.

A little background: We have a small personal network with only Mac and PC computers both accessible to one another thru a common WiFi and set permissions between the computers. With Finder I can use Ctrl-K to add any PC on our network and open and drill down to look at the user's files, desktops, documents, etc. Thanks to permissions granted on the PC, I can also edit, delete or modify the PC's files as well. Now when I open Finder, the connection to the PC ("hnk2011") remains available under "Shared" header along with a few network printers (screenshot attached).

When drafting an email however, these "Shared" header is not visible in the Attach file menu and is also not listed under the "Devices" header (screenshot attached). Where did "hnk2011" disappear to? How do I find it?