After you upgraded from a Typo3 Version 4.5 LTS to Version 6.2 or higher you may wounder why the backend search is not working anymore as expected. Even in the list mode the result of extension records can be empty.
If it’s your own extension you can fix it very easy. Since Version 4.6 the search behavior was changed (see https://forge.typo3.org/issues/36452).
To re-enable the search function of your own extension records to have to add this line to your ext_table.php:
$TCA['name_of_table']['ctrl']['searchFields'] = 'col1, col2, col3';
Just include all columns which make sense. Clear the system cache and it’s done. Of course you need to do this for every table which you wanted to be searched 🙂