Retrieve the Query Builder after filtering the results

To retrieve the Query Builder after filtering the results: you can use ->toQuery().

The method internally use the first model of the collection and a whereKey comparison on the Collection models.

// Retrieve all logged_in users
$loggedInUsers = User::where('logged_in', true)->get();
 
// Filter them using a Collection method or php filtering
$nthUsers = $loggedInUsers->nth(3);
 
// You can't do this on the collection
$nthUsers->update(/* ... */);
 
// But you can retrieve the Builder using ->toQuery()
if ($nthUsers->isNotEmpty()) {
    $nthUsers->toQuery()->update(/* ... */);
}

Tip given by @RBilloir