Currently you have to hit F12 to get a screen shot. View > Recordings/Screenshots then upload it to steam. Then close the recordings/screenshots window because it doesn't update till you close the window, go back to view > Recordings/Screenshots click the image you already shared again and view on steam which closes out the form you are on to then click share to get the URL and go back to the form post hit edit add the URL. And do this for each and every shot.