I would recommend differentiating the role and the level. A level could go: Junior > Advanced > Senior > Staff. Roles could be: Tester, Automation Engineer, Lead, etc. So you can have a Senior Tester as well as a junior lead. These are all individual contributors - without hire/fire and staff responsibilities. That would be a separate role: the management track. To design a test department, I would recommend looking into Team Topologies.