We would like to have a new softkey on the IP phone that will allow the users to activate and deactivate the alternate greeting from the softkey instead of having to go inside the voice mail box and activte the alternate greeting.
I'm assuming you want the softkey to show up on the native call plane--then the answer is no, you can't add new softkeys.
Your closest workaround is to configure an HTTP Speed dial on the phone, and that speed dial would need to hit a custom application, which does the legwork to talk to Unity and make that happen programmatically (not even sure if that's possible).
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.