Hi ,

To edit the name of an existing group in Odoo 15, you can do it directly from the UI by following these steps:

1. Log in to your Odoo 15 instance as an administrator.
2. Go to Settings → Technical → Security → Groups.
   (Make sure developer mode is enabled to see the Technical menu.)
3. Find the group whose name you want to change and click on it to open the form.
4. Click the Edit button at the top right.
5. Update the Name field with the new group name.
6. Click Save to apply the change.

Note: If the module that defines this group is updated or reinstalled, your changes might be overwritten. To make permanent changes, you may want to override the group’s XML in a custom module.

For more details on overriding security groups, check out this blog:

How to Override Existing Security Groups in Odoo 15

Hope it helps