how do I restore the Download stack in the iMac Dock? Download stack is missing from the iMac Dock. The Download stack was originally present but may have been removed with the High Sierra update. Presently all downloads go directly to the download file and plus be recovered from the Finder application. I have not been able to find guidance on how to solve this problem in the Safari help.
Open Finder and go to your home folder using the go menu. 
Drag the Download folder to the dock to the immediate left of the trash. 
Control click the downloads to choose the stack effect if needed.