If you have a Pentaho BI Server running, the test tab can be used to test your action sequence against the running server. Simply enter the URL to the running Pentaho server and select "Run". Your action sequence will be submitted to the server for execution and the results will be displayed within the tab.
Templates are a great way to get a jump start on building action sequences. If you find that you're repeatedly creating action sequences with a similar set of steps, this might be a good candidate for an action sequence template. To create a template simply create an action sequence containing the basic steps and save it to your project. Make sure that on the General tab you give the action sequence title uniquely identifies the template. Now copy this new action sequence into the <eclipse_install_dir>/plugins/org.pentaho.designstudio.editors.actionsequence_x.x.x.x/templates directory. Next time you create a new action sequence, the Action Sequence Wizard will include your action sequence in the list available templates.