When you run a Ruby script, Rails server, test, or other command, RubyMine automatically creates a corresponding temporary run configuration. Such configurations are greyed out in the list of the available configurations.
By default, there can be created only five temporary configurations per project, so when you create the sixth configuration, the one created first gets removed, and so on. You can change this limit in the Temporary configurations limit field in Edit Configurations | Templates.
Save a temporary run/debug configuration
In the Run/Debug Configuration selector, choose .
In the Edit Configurations dialog, select the temporary configuration in the list, and click .
From the context menu of the editor or Project tool window, choose .