In your ProductResource.php form() method, update the FileUpload field like this

FileUpload::make('image')
    ->label('Imagen')
    ->avatar()
    ->required()
    ->afterStateHydrated(function (FileUpload $component, $state, $record) {
        if ($record && $record->mainImage()) {
            $mainImage = $record->mainImage()->path;
            $component->state($mainImage); // Set the existing image path as the field value
        }
    })
    ->getUploadedFileNameForStorageUsing(function ($file) {
        return $file->store('products', 'public'); // Save the file to the public storage
    })
    ->directory('products') // Optional, for organized storage
    ->deleteUploadedFileUsing(function ($file) {
        \Storage::disk('public')->delete($file); // Delete the image from storage if replaced
    }),

how it would work

• The ->afterStateHydrated() method checks if there is a record and a primary image.
• If the mainImage() exists, it sets the path as the state of the field using $component->state($mainImage).
• This will automatically bind the uploaded file to the field state and display it as if the user had uploaded it.
• The getUploadedFileNameForStorageUsing() method makes sure the file is stored correctly under the public/products folder.
• The deleteUploadedFileUsing() method will delete the file when the user replaces it.

Optional: Validation If you want the field not to be required when editing, only when creating, you can add

->required(fn ($record) => $record === null)

Now,

• The image will display in both Create and Edit forms.
• The image will be correctly bound as the field's state.
• Users can update other fields without having to re-upload the image.

let me know if it works for you?