Exporting to CSV isn’t a feature that is included in the plugin, but depending on your needs and expertise you may still be able to get what you are after.
The ‘basic’ information like the URL, the desktop/mobile page speed scores, page type, etc are all stored in the database table wp_gpi_page_stats (wp_ being the default wordpress db table prefix).
Most hosting providers give you access to the database in one way or another. A really common method is through some software called phpMyAdmin. Pretty much any DB software will let you export that table to a CSV, and choose which table columns you want to appear in your CSV.
I hope this helps!
