This can be achieved through feature control policy.
Under Device->Device Settings->Feature Control Policy->Add New
Select which softkeys you want to appear on the phone such as Divert (Alerting) and Divert (Connected) , Save the policy.
On the device configuration under Device->Phone, specify the name of the feature control policy you just created for each DX650.
Reset the device.
Thanks for this, and I have created, but I stil dont get Call Divert as an option.
Although when I now decline, it seems to be attempting Voice mail but fails. If I decline in Jabber, for the same call, it goes striaght to Voice Mail !! So dont see it as a CSS issue.