Editing agent notification schemes is not yet available in next-gen (for example: configuring a notification scheme that will alert agents on issue creation) but you can achieve this with automation rules.

Work around

Please refer to this community post https://community.atlassian.com/t5/Jira-Service-Desk-questions/Next-gen-Service-Desk-Issue-Created-Notifications/qaq-p/1136149 or download the attached PDF as a work around and see below screen.

Disclaimer: You have to maintain the user list in the automation setting.