You can do this using the backend files BUT you must be careful when doing this. The backend files are just XML files. The ones you want to look at are the .item files. You can find your jobs inside the workspace/{project}/process folder. To do this safely I would copy your workspace folder to another location (to ensure you don't accidentally change the original files). Then all you need to do is recursively look through your process folder (you can use a tFileList for this) and then read the files using an XML component, looking for a path of talendfile/context/contextParameter. All of your context variables and their original values will be stored there.
In fact, you can find out absolutely anything about the jobs you have built using these files. You just need to learn how to use and to NEVER EDIT THEM.
