It is a really strange issue. On the screenshot I see that you do not have the folder "Configuration" under "Library". The configuration is part of the platform and the workflow "Import certificate" should be there.
Can you please check if you have the file "o11nplugin-configurator.dar" in the folder /usr/lib/vco/app-server/plugins?
Something that you could try is:
1. Login into Web Configurator of vCO
2. Go to Troubleshooting and click on Reset current version
3. Restart vCO
This will upload plug-in's content to vCO database on restart
Hope this helps
You can duplicate the workflow, then edit the new created workflow, and change the "import a certificate from URL" task with the workflow you have in vCO.
Then run the new workflow.