I don't believe this setting can be changed by yourself.
Also note, from the same linked help page, "If you have enabled the option to permanently remove deleted messages within the email settings, you will not be able to recover the message once it has been deleted. It is recommended that you do not use this setting."
Don't move messages to the Trash folder unless you are absolutely certain you will not need them again..
It's What I Do. I Drink and I Remember Things.
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