It would be great if we have a feature to disable sending emails when assigning users/groups to project roles, or to see a checkbox like ‘notify the users’.

NOTE: We are currently rolling out the feature of sending emails with the title '<User Name> invited you to <Project Name>' to users who are assigned to project roles in business projects. However, It’s still an experiment at the moment, so some users may not yet be able to use the feature of sending emails.