The codex page for Media Library Screen says that the table of media includes a column called "Description - The description of the Media you assigned at the time of upload."
There is no "Description" column in the Media Library Screen.
Either the codex needs to be updated, or the code needs to modified to include the Description in the table.
My vote goes to the later.
Note: this codex error has existed for a while> It is NOT new to Vn 3.9.