You will need PHP skills to accomplish this. If you are familiar with PHP, consider checking out this parallel thread, where a similar modification is discussed:
I made some changes in php code of FileManager.inc.php and ArticleFileManager.inc.php to limit uploaded supplementary files type to zip files (as we want our authors to send all necessary files packed in one zip or tar.gz file).
And this works - I mean the OJS uploads only zip files (I used unzip shell command to test the file).
But the problem is that even if the file is not uploaded, because of the invalid format, OJS numbers it and displays on the list of article’s supplementary files as t…