Send Custom Notifications with Flow Builder
Where: This change applies to Lightning Experience in Essentials, Professional, Enterprise, Performance, Unlimited, and Developer editions. You can send notifications to desktop users in Lightning Experience and Salesforce Classic in all editions and to mobile users in the current Salesforce mobile app in all editions, except Database.com, and the new Salesforce mobile app in all editions, except Essentials and Database.com. You can also send notifications to users in Mobile Publisher apps for an extra cost.
How: In Setup, search for Notification Builder and create a Custom Notification Type.
Then add the Send Custom Notification action to an action in Flow Builder, and select your Notification Type ID.