Thanks for your question. I am not familiar with the “wp-media-library-categories” plugin so I don’t know all the possible complications with MLA. However I can answer your specific question, “I wonder if there is a method to disable the search box of the media library assistant in the wordpress media library“?

You can try disabling some MLA enhancements instead of deactivating MLA completely. Go to the Settings/Media Library Assistant General tab and scroll down to the “Media Manager/Media Grid Enhancements” section, then uncheck the first two boxes to prevent MLA from downloading any JavaScript for the search box to your browser. You can also disable some of the enhancements individually if that suits you. Scroll to the bottom and click “Save Changes” to save your work.

I hope that gets you the results you need. I am marking this topic resolved, but please update it if you have any problems or further questions regarding the above suggestions. Thanks for your interest in the plugin.