Here's how I deal with such situations.

First, I create a "CSV" entry with the "primary keys" (which I also use for sorting) then, I list all the records.

foo.files=f1,f2
foo.files.f1.name=foo.txt
foo.files.f1.expire=200
foo.files.f2.name=foo2.txt
foo.files.f2.expire=10