Yours truly for iMore:
In iOS 15.4 beta 1, Apple has added a new toggle to Personal Automations in the Shortcuts app for “Notify When Run.”
[…]
With the new “Notify When Run” toggle, Shortcuts users can toggle off the setting to notify them when the shortcut is run, meaning you won’t actively be alerted each time the automation trigger is met.
Shortcuts automations are becoming more seamless and will soon truly work in the background – it’s time to take more advantage of Personal Automations.