Attempt to generate a calculated file name via “Plugins-Page-Design-Settings-File Name” for the export PDF. According to the manual, using values is possible via column names in curly brackets.
Test 1 (date of creation, calculated from the creation timestamp (YYYY-MM-DD) fails.
Test 2 (simplified, only extraction of the year as YYYY) also fails.
The value does not show up but is visible correctly in the corresponding row/column. Both tests also covered whether the field must be used in the report or not. All combinations led to the same erroneous results: A calculated field is not displayed/used (also no space).
I got interesting results!
When creating a PDF via a button, link, formula, and link formula columns can be cited in the PDF file name. In the screenshot below, {Date} is a formula column and {Customer} is a link column.