Unfortunately, the code editor is IonCube encoded, which makes it rather opaque:
/usr/local/cwpsrv/var/services/users/codeEditor.php
Maybe you could use a browser plugin to flip the form control around:
<select class="form-control" onchange="selectTheme(this.value)" data-ddg-inputtype="unknown">
<option value="default">Light Mode</option>
<option value="monokai">Dark Mode</option>
</select>
Meanwhile, if you want to fix the English grammar of the File Manager interface, the file to edit is here:
/usr/local/cwpsrv/var/services/users/cwp_lang/en/filemanager.ini