Set default export directory

<?php

namespace App\Models;

use App;
use Filament\Actions\Exports\Models\Export as BaseExport;

class Export extends BaseExport
{
    public function getFileDirectory(): string
    {
        // build full path here
        $fullPath = ....
        return $fullPath;
    }
}

// Bind custom Export model for Filament exports
$this->app->bind(
    \Filament\Actions\Exports\Models\Export::class,
    \App\Models\Export::class
);