In order to export all callbacks (CBHOLD) from the entire dialer, please log into the MySQL and run the following query:
SELECT * FROM `vicidial_list` WHERE `status`='CBHOLD' INTO OUTFILE '/var/www/html/vicidial/cbholds.zip' FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' LINES TERMINATED BY '\r\n'
After that, navigate to http://your-dialer-addres/vicidial/cbholds.zip, download and rename the file from .ZIP to .CSV.