If you wanted to add a new variable to the templates in service to a new feature you have built then you can add the variable in the following way:

To make the new variable available to the autoscaler,on the build machine repository, add the new variable to

 ${BUILD_HOME}/builddescriptors/autoscaler_descriptor.dat

To make the new variable available to the webserver on the build machine repository, add the new variable to

 ${BUILD_HOME}/builddescriptors/webserver_descriptor.dat

To make the new variable available to the database on the build machine repository, add the new variable to

 ${BUILD_HOME}/builddescriptors/database_descriptor.dat

NOTE: there needs to be an empty line at the end of each file so that all of the lines are read by the script

It is then a development task as to how to access the values of these variables which are stored in

 ${HOME}/runtime/autoscaler_configuration_settings.dat on the autoscaler 
 ${HOME}/runtime/webserver_configuration_settings.dat on the autoscaler

 ${HOME}/runtime/webserver_configuration_settings.dat on the webserver

 ${HOME}/runtime/database_configuration_settings.dat on the database