quicksearch layout folder has not changed and will load the contents prior to this release/redesign.
Although it has not moved to a different lcoation, this component has gone through significant UX/UI changes that cannot be simply overridden by your current code (prior to 12.3).
You must, manually, move your customizations prior to 12.3 quicksearch to 12.3+ quicksearch by adapting your code to the new handlebar template, JavaScript and PHP code.
Handlebars Customization
If you have overridden handlebars template /custom/clients/base/layouts/quicksearch/quicksearch.hbs, you must take the redesigned component from /clients/base/layouts/quicksearch/quicksearch.hbs and re-apply your customizations to on your custom code.
Javascript Customization
If you have extended javascript /custom/clients/base/layouts/quicksearch/quicksearch.js, using the extendsFrom, your customization should work.
If you have overridden javascript /custom/clients/base/layouts/quicksearch/quicksearch.js,you must take the redesigned component from /clients/base/layouts/quicksearch/quicksearch.js and re-apply your customizations to on your custom code, however, if you did this, it's wrong and you should use the extendsFrom as it is our recommended best practice.
PHP Customization
If you have overridden PHP metadata /custom/clients/base/layouts/quicksearch/quicksearch.php, you must take the redesigned component from /clients/base/layouts/quicksearch/quicksearch.php and re-apply your customizations to on your custom code. The order of elements have changed and are important for the redesigned component.