I think you will have to determine if you have your workflows somewhere in a physical way and try to import them as folders as I have show.
You might want to do this on a fresh system since it might come to a point where you will need desaster recovery from your hard drive in which case it is best to not further interfer with the hard drive further.
Is is possible you have used your (online) git repository to overwrite your local workflow directory.
KNIME analytics platform does not (yet) have a recycle bin or its own backup system. You have to backup your work yourself and no clever trick from the forum will bring it back by itself.
Also it would be great if you could directly respond to suggestions being made so we can further explore what is going on.