How to store secrets longer than 4096 chars?

Prerequisites

• I am running the latest version. (up upgrade)
• I searched to see if the issue already exists.
• I inspected the verbose debug output with the -v, --verbose flag.
• Are you an Up Pro subscriber?

Description

I am trying to provide certificates to my service, but up's method for storing secrets (encrypted environment variables) doesn't support strings of this length (> 4096 chars). How should I store lengthy secrets?