I would like to change the access rights for cases from the same workflow, what are the options?
You have different options for the access rights. You can find all details in the user guide: https://docs.signavio.com/userguide/workflow/en/access.html#restricting-access-to-user-tasks
KBA , BPI-SIG-CA-SEC-UM-AM , Access Management for SAP Signavio , How To
SAP Signavio Process Governance all versions ; Workflow Accelerator by Signavio all versions