tachiyomi/app/src/main/res/menu/extension_main.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/action_search"
        android:title="@string/action_search"
        android:icon="@drawable/ic_search_white_24dp"
        app:showAsAction="collapseActionView|ifRoom"
        app:actionViewClass="androidx.appcompat.widget.SearchView"/>

</menu>