The 'Edit' button is not present when attempting to modify or verify a PXE boot configuration. Only the 'Redirect' button is available.
Release : 3.3
The scope of the configuration is 'Shared' which is not editable when a specific PXE server is selected
1) From PXE Configuration Utility go to File > Choose PXE Server
2) Select 'Shared Configuration'
3) click 'Open'
You should then be able to select the desired configuration and select the 'Edit' button