How to remove launch configuration histories in eclipse?

This question seems to be well answered here, however, to make changes I have simply deleted every undesirable launch configuration from the below path.

${WORKSPACE}/.metadata/.plugins/org.eclipse.debug.core/.launches/Delete all the .class LAUNCH Files

After deleting the files, it is necessary to restart Eclipse for the changes to take effect.

Under Window...Preferences...Run/Debug...Launching...Launch Configurations, you can activate and deactivate some filters that restrict what is shown in Run...Run Configurations. I think it is what you are looking for.