Hi Maryna,
While there is admittedly a known bug with this feature in the 2.7.1 release (which has already been addressed internally - see #
13659), there is already a way to do this via the user interface that might be much simpler. See step 6 in this section:
This method uses PHP code to handle the criteria (keeping it much simpler), and also includes some basic protections so you don't export a CSV that cannot be reimported (in that if you want to export a descendant level, then all ancestor levels above it must also be included, so no records are orphaned without their parents).
Doing this via the criteria option on the command-line would involve a number of joins across both the term (for Levels of description) and object tables (for object IDs etc) - meaning it may be rather complex to craft, and somewhat fragile. It's certainly beyond my own meagre skills to construct, unfortunately.
I am wondering if you might meet your needs by either using the functionality supported via the user interface, and/or exporting all records and then sorting by level of description in a spreadsheet application (like LibreOffice Calc, etc) afterwards, deleting the rows with levels you don't want? If no, perhaps you can tell us more about your use case?
Cheers,