Thinking a bit more about it.. one can only expect env placeholders for string values. Maybe having specialized builder API is the better approach, think;

->ifEnv()
->ifNotEnv()
->ifArrayEnv()
->ifNotArrayEnv() // we need this one for e.g. trusted_hosts instead of isString()
->then()

@ro0NL for me seems ok.

@stof @ro0NL Hi! Do you need any assitance on this ?
I'm currently facing the exact same issue as mentionned in #28137 (i.e. being able to configure the delivery_addresses of swiftmailer from an env var of varying size between each env).

@ro0NL What's the status here?

@fabpot it's kinda on hold, but we can discuss further in #27683. Closing as such.

What i particularly dont like about this implementation is, each affected node having to handle the case themselves, i.e.;

->beforeNormalization()
    ->ifString()
    ->then(function ($v, bool $isEnv) {
        return $isEnv ? $v : array($v);
    })
->end()

It hurts maintenance. I prefer something generic that just works, but i dont know how to do it.