Using multiple boot traits with the same event will fire just the first one and ignore the rest bootable traits.

class Tag extends Model
{
    use HasKey; // this will work (but if i put it bellow it will not work)
    use HasSlug; // this's not (but if i put it above it will work)
}

trait HasKey
{
    public static function bootHasKey()
    {
        static::creating(
            fn (Model $model) => $model->key = 'value'
        );
    }

trait HasSlug
{
    public static function bootHasSlug()
    {
        static::creating(
            fn (Model $model) => $model->slug = 'value'
        );
    }
}