Dashboards be it Project or Team can be edited only the Project or Team admins in Azure DevOps. But you can also give permissions to certain users to edit the Dashboard. To give edit permissions you must be either a Project or Team admin and you should also have Basic level access. Then follow the below steps to give edit permissions
Step1: Go to Overview –> Dashboards
Step2: Click on the “3” dots next to the Dashboard for which you want to give edit permissions
Step3: Then in the next screen, enter the user for whom you want to give the Edit permissions
Step4: Select “Allow” against the Edit dashboard permission
Now the user will have access to edit the specific Dashboard. This access is only for a specific dashboard, incase if you want to give edit access to a user for multiple dashboards, then create a group, add the user into the group then add the same group into different steps by repeating the steps above.