FFCore will add content from the manifest to the press sheet. As such, you would need to put the manifest filename in the manifest itself.
If you cannot do that upstream then you can enable prescripting and write a small script to add the manifest filename to the manifest.
We do not have a variable for the filename but the above should get you there.
I would to have the press sheet name show the name of the manifest we are using. It is currently using the name of the last filename in the .CSV file. Is there a way to fix this?