Often I’m faced with a choice of declaring a private function in a companion object (good for encapsulation) or at the top file level (reduces indentation). Which do you prefer?

class Foo {
    companion object {
        private fun bar1() { ... }
    }
}

private fun bar2() { ... }

private fun Foo.Companion.bar3() { ... }

1️⃣ companion object 2️⃣ top-level (file) 3️⃣ top-level companion extension

2️⃣ for me, the only drawback is that https://youtrack.jetbrains.com/issue/KTIJ-11292 is not done yet

if it private as in your case, I always prefer member function:

class Foo {
    private fun bar1() { ... }
}