How to register a new conversion without adding it to the queue?

[animesubindo181225]

Conversion for mp4 files to webm for media triggered from \Spatie\MediaLibrary\MediaCollections\Events\MediaHasBeenAdded was successful with and the generated_conversions field in the media table became:

{"webm": true}

When I try to get the URL for the file converted with $mediaItems[0]->getUrl('webm'); I get the error:

{
    "message": "There is no conversion named `webm`",
    "exception": "Spatie\\MediaLibrary\\MediaCollections\\Exceptions\\InvalidConversion",
    "...": "..."
}

I tried to register the media conversion as below, but by adding that line, every time I add media, a new job Spatie\\MediaLibrary\\Conversions\\Jobs\\PerformConversionsJob is added to the queue, and when the job is processed the image file with the extension .webm created/added to the conversions folder.

public function registerMediaConversions(Media $media = null): void
{
    $this->addMediaConversion('webm')->withoutManipulations();
}

How to add media conversion without action (so that no jobs are added to the queue)?

I have also tried the following function but the job is still added to the queue

this->addMediaConversion('webm')
    ->removeManipulation('format')
    ->removeManipulation('optimize')