The easiest way to do it is getting another of your scrum masters to give you the role back.
The alternative is raising a support ticket with Mendix.
Hope this helps
What if your are the only scrummaster. Is there another way besides a support ticket?
As mentioned by the other commenters, you can only have another scrum master change your role. If you are the last remaining scrum master in the team and have accidentally changed your role, our support team can change it back for you.
We are aware of this bug and and are working on a fix to prevent users from changing their role when they are the last member and automatically restore the scrum master role of affected users.