I'm using a moto G (2015) which has android 6 stock. There is no button to clear all apps launched. By "clear" I mean quit and delete cache. Some skins have such button sometimes represented by a carpet sweeper icon.
I know there is no need to clear opened applications. Android is managed them, will clear them for you if needed, and if you quit an app manually, she will be slower to open.
But I don't like to have a list of recently opened apps (in order) available to whom take my phone. Sometimes, the browser (firefox) remember my last search and I don't want that (I use also inbrowser but needed firefox for the sync feature).
Is it a simple way to add a clear button to android stock?