Hello and welcome! So that we can better help you, please clarify which device are you referring to. Also, in order to continue participating in this conversation, you may want to consider registering for an account here on Android Central. If you're interested in registering for an account, you'll find instructions here: https://forums.androidcentral.com/ask-question/409154-join-android-central-community.html
Kotlin is a programming language that can be used to develop Android apps. I'm guessing the OP is asking how to assign a button (either onscreen or physical) to open the App Overview.
I moved this to the Software Development forum for more specific traffic.