Unfortunately Sybase Central is not supported anymore. It has not been released since the old Sybase Replication Server 15.7 which is no longer supported (SAP calls SRS 15.7 but in reality it is 15.7.1) .
There currently is no GUI tool to do this at this time. If the Sybase Central functionality is something you would like to see back in the product please go to the following Replication Server Idea Space to request new functionality and vote for features other users have requested that you like. The more people vote on a feature it will be discussed with engineering about getting it added to the product.