When you load an Automap wrapped instance of Reaktor the controls in Automap will be labeled 'P0001', 'P0002', P0003' etc. These numbers correspond to the Automation IDs of the parameters of the ensemble you load in Reaktor. It is unlikely that the parameters will be mapped intuitively to the controller and you will probably want to remap them. You will also probably want to rename them so you can identify the control by name rather than number. Consequently after loading an ensemble you can 'clear all' controls and start relearning them in a way that better suits you. When you relearn the controls you will see that the name displayed in Automap is now the parameter label as defined within Reaktor and not the parameter automation ID. Note the parameter label is not what it is labeled on the ensemble GUI but is set in the options for that parameter. You may still wish to rename the controls in Automap as the parameter labeling within the Reaktor ensemble may not be simple to understand or there may be parameters with identical labels. You can do this by typing a new name into the name box in the Automap GUI.
Once you have learned all of the controls for an ensemble or instrument you can save the mapping as a *.automap file by clicking in the Automap File menu and selecting 'Save...'. The 'Save As Default' function will not be particularly useful with Reaktor because the mapping for one ensemble will not suit any other ensemble. Therefore there is no suitable default mapping, unless of course you use one ensemble more than others. The best system to use is to load an Automap wrapped version of Reaktor, select the ensemble you want to use and then load in the relevant *automap file for that ensemble (if you have created one) by clicking on the Automap file menu and selecting 'Load...'.