Hi rasmus_kjaer,
I took a look but unfortunately I'm not seeing any guides or information available in which the plagiarism review settings can be changed at an admin level.
If you're using TII, which would have that show report setting as an option, there should be a checkbox at the teacher level when viewing the assignment edit page to save the current settings as default settings. However, I'm unfamiliar with any way you can achieve this at an admin level for all teachers.
You may need to reach out to Canvas support with this question, as it may be something specific to your plagiarism checker's installation, or something setup when the checker is connected to your instance.
