That constant is defined in the ajax-search-pro\includes\classes\core\class-asp-manager.php file within this function:
Is this not the correct way? Please let me know, I am not too familiar with these modifications myself.
Also, from what I can see in these docs, if the UPLOADS constant is set in the wp-config.php file, the wp_upload_dir() will return that url relative to the ABSPATH constant. You might need to set that constant as well, I am not sure.
Let me know!Best,
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