You should be able to set the value fParentGUID and this will set the folder. This works very similar to how xCollectionID (folders_g) worked.
These two links should be of help:
As Jonathan mentioned you can replace the xCollectionID with fParentGUID in your Rule and it should work the same way as it worked with folders_g. Please note the fParentGUID is the folder ID in FrameworkFolders and it looks something like this '02A346449F7EF0456C5C3AE2C2DB5A89'. You can get this info on the folder info page with &IsSoap appended to the URL.