To use the custom replacements function yoou will need to update the notification extension cerated in the previous step, here are the steps to follow.
1. Create an app group identifier
Go to developer.apple.com -> Certificates, Identifiers & Profiles -> Identifiers. Select App Groups and create a new one.
2. Enable App Groups
You will need then to enable app groups, with the app group created previously, both on developer.apple.com and on the project in XCode, under the Signing & Capabilities section.
You need to do this for the main app and for the notification extension.
3. Set the app group identifier
In your AppDelegate class set the app group identifier