Alfred's workflows can include an "eject all" system command. I've set up a keyboard shortcut to eject all my drives, for easy use when I want to unplug the laptop.
It certainly works, but some drives take longer than others—mechanical disks might need to spin up (my RAID takes a while)—so it varies a lot. Sometimes the notifications flick by in rapid succession (replacing each other, so you only see the most recently ejected), and sometimes you wait 10 seconds. Sometimes a disk won't eject, times out, and you get that pop-up.
Obviously Alfred is tracking its attempts t