You can manually delete the physical log files via FTP by deleting the sub-folder(s) inside the /wp-content/uploads/wpallimport/logs/ folder. As for the history log entries in the database (what you see on the "History Logs" page), you'll need to run an SQL query to delete them in bulk (you can run queries with this: https://wordpress.org/plugins/ari-adminer/). For example:
DELETE
FROM `wp_pmxi_history`
Some things to keep in mind here:
-
Always back up your database before deleting things like this.
-
This deletes all history log entries for every import. Add a WHERE clause to specify an import ID if necessary:
DELETE
FROM `wp_pmxi_history`
WHERE `import_id` = '2'
- Change the "wp_" prefix if you use a different one in your install.