By design, only Supervisors and Time Approvers can approve time entries of their subordinates. However, this only works if the user is using the Employee Center role.
A custom role with Track Time permission with at least Create level of access can approve time entries of all employees by navigating to Transactions > Employees > Approve Time. This imposes a problem to the company since even non-supervisors can approve time. Also, when a user enters a time entry, the Supervisor Approval checkbox is available, which when marked approves the time entry.
There is no separate permission to approve time entries. There is an enhancement logged under Issue 163690.
To resolve this, the Supervisor Approval checkbox must be hidden on the time entry form for the custom role:
1. Navigate to Customization > Forms > Entry Forms.
2. Customize the Time Tracking Form.
3. Navigate to Fields tab.
4. Unmark the Show checkbox for Supervisor Approval.
5. Click on Save.
Next, the Employee Restriction on the custom role needs to be set to own and subordinates only. This restricts them from viewing and approving the time entries of other users.