In Web TimeSheet it is possible to allow supervisors  to edit the Expense sheets that are waiting for their approval. To do this please follow these steps:

1] Log into Web TimeSheet with administrative rights.

2] Click on 'Administration' icon at the top.

3] On the left side pane, under 'Users/Departments' click on 'Permissions'.

4] Click on the edit button next to the required permission.

5] Under 'System' expand 'Approvals', under 'Expense' make sure 'Edit' is checked.