Coffee

This Android app allows you to keep the display awake without having to change the device settings. It can be toggled at various places:

A tile in the quick settings, the place that holds the toggles for e.g. Wi-Fi and Bluetooth. Requires Android 7 or higher.

A button in the app itself

A shortcut on your home screen. It can be created in the app, if your launcher supports it.

Coffee can be set as assist app (Device settings => Apps => Default apps => Assist app) and changes it's state when assist is called.