You can change the notification with help of described examples.
Episerver has ProjectEnhancements on Github. A good source if you need code examples.
I've looked into this not too long ago, and found there's not a ton of flexibility with how the actual email template can be modified. See this post: https://world.episerver.com/forum/developer-forum/-Episerver-75-CMS/Thread-Container/2020/11/approval-sequence-customisations/#230497
Copy/paste from that thread:
"I dug into this a bit, and there's not a super simple way to do it. The actual email template is an embedded resource, and the call to get the template is internal. To get started, you'll need to create a custom formatter (INotificationFormatter) as explained here: https://world.episerver.com/documentation/developer-guides/CMS/using-notifications/usage-examples/. From here, I would suggest digging into this more by decompiling the class "ApprovalHtmlEmailFormatter" in the EPiServer.Cms.Shell.UI.Approvals.Notifications namespace, and looking how the FormatMessagesAsync() is done."
We are new to Episerver and I was not able to find where can I change this notification? How and where can I change the text for the message? Is this customizable out of the box? Any suggestions are grately appreciated.