I’ve created a new user with it’s own home directory and disabled root. However, when I did this, I lost the dietpi startup script. I tried sourcing it from my .bashrc but this require I sudo and provide my password again.
Basically, my question is: what do I need to my new user to ensure it has access to all of the dietpi tools and configuration?
You should still be able to use diet-pi commands along with “sudo” as all the commands are tied back to the root user. I have made my default user and disabled root access through ssh and only use it sometimes. “sudo dietpi-launcher” is the only real command you need to remember as you can access all the other commands from the menu that pulls up.
Spot on 
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By using the launcher with sudo, all DietPi Programs will be launched with the required root privileges.