custom output for boolean columns export

I have boolean columns in my db, when I export I want to replace boolean with custom words like YES/NO

Is that possible?

Yes. You can do something like this

(new FastExcel(User::all()))->export('users.csv', function ($user) {
    return [
        'my column name' => $user->myBooleanVariable ? 'YES' : 'NO',
        // Then the rest of your columns
    ];
});