Hi @Roger Roger,
Welcome to the Microsoft Technical Support Forum.
According to your description, you want to create a custom role for users to manage M365 groups, distribution lists, dynamic distribution lists, mail-enabled security groups, shared mailboxes, and conference room mailboxes in M365. In addition, you do not want users to make any other changes in the Exchange Online Admin Center.
After my research, the custom role operation is not currently supported, but there are administrators who can complete some of your requirements, but they cannot be accurate to your needs. You can try the following steps to manage and assign role permissions:
- Manage M365 groups in M365 In the Microsoft 365 adimin center, navigate to Roles—>Role assignments—>Groups Administrator, and assign permissions to the users you specify as shown in the following screenshots.
- Manage distribution lists, dynamic distribution lists, mail-enabled security groups, shared mailboxes, and conference room mailboxes.
a. Create a new role group in the Exchange Online Management Shell
New-RoleGroup -Name "Group and Mailbox Manager" -Roles "Distribution Groups", "Mail Recipients", "Security Group Creation and Membership"
b. Add members to the role group
Add-RoleGroupMember -Identity "Group and Mailbox Manager" -Member <user-to-add>
If you have any questions, please feel free to contact me.
Best regards,
Jake Zhang