How do I assign the double click side button to App Switcher?

rob5i wrote:

[You can’t change it.]

You can assign it for Apple Pay. That's a change.

[you shouldn’t need to use the app switcher that often]

WhatsApp does not currently have the ability to translate so it's necessary to switch between Translate and WhatsApp constantly. WhatsApp is used widely in Spain for nearly every kind of booking.

Which is why I said just swipe the bottom bar left or right to switch between 2 apps

[you should not be removing apps using the app switcher]

Apps running in the background are a draw on the battery.

FALSE. The App Switcher does not show apps running in background; it only shows apps that have been used recently. None of them are running. All but the 3 or 4 most recent aren’t even in RAM. And killing them in the app switcher actually uses more energy that just leaving them there; killing an app takes energy, then reloading it when you want to use it again also takes more energy than just restarting it. Here’s more details→Do not close "background" apps | Communities

You can’t change it. But you shouldn’t need to use the app switcher that often. To switch between recently used apps just swipe the bottom bar left or right. And you should not be removing apps using the app switcher, except in the rare case of an app that is not working properly.