Hello all,
With the implementation of JSM we have probably exhausted the possibilities of notifications.
We use the customer notifications, the project notifications as well as the possibility to trigger emails via automations (action: "send mail").

Now we still have the problem of double notifications.
(About the process: there is a JSM ticket, this is transferred to the next status and with this a Jira ticket is created. These are linked together and are synchronized). I.e. if a comment is written in a JSM project, it will be transferred to a Jira project and vice versa. By removing the Request Participants (only certain user groups) at the status transition, we stop the duplication of emails.
The problem is the reporter. This person continues to receive notifications even though they are in the group to be removed. Unfortunately, I have not found the way to build a rule that sets the issue property accordingly (or something else).
(In notifications, the field with the bell in the settings (/jira/servicedesk/projects/project/settings/customer-notifications/template) can be addressed with the variable "${request.disable.notifications.url}"). 

Request:
The button (bell) "Notification on | off") can be addressed via automation. (e.g. trigger: issue created, user condition: [user: reporter | is in group | criteria: group), action: set entity property of "bell" // OR action: edit issue of field "bell")