If you want the button to show up in the right-click menu of all contacts then you'd add the new button here:
/ZimbraWebClient/WebRoot/
js/zimbraMail/abook/controller/ZmContactListController.
js
ZmListController.prototype._contactOps =
function() {
var list = new Array();
if (this._appCtxt.get(ZmSetting.SEARCH_ENABLED))
list.push(ZmOperation.SEARCH);
if (this._appCtxt.get(ZmSetting.BROWSE_ENABLED))
list.push(ZmOperation.BROWSE);
list.push(ZmOperation.NEW_MESSAGE);
if (this._appCtxt.get(ZmSetting.CONTACTS_ENABLED))
list.push(ZmOperation.CONTACT);
return list;
}
You'll need to add the ZmOperation first if it's a new operation.