I generally set "Message level" to "Errors and Warnings" because of the constant spam of "Creating delivery from X to Y..." when at the "Notifications level".
One message that I really would like to see at the warning level is "No train to transport x to y found...". It's an important indication to me that I need to make more trains and depots available.
Feature Request: Set "No train to transport..." to be a warning level message.
Moderator: Optera
Re: Feature Request: Set "No train to transport..." to be a warning level message.
I recommend LTN Tracker for your intended use.
My Mods: mods.factorio.com