You could make a cheats text file with cheat codes in it. Make sure you use the right version of a code. Mario kart 7 has v1.0 and v1.1. If you're updated then it's v1.1
SD: luma/titles/0004000000030800/cheats.txt
https://github.com/LumaTeam/Luma3DS/wiki/Cheat-Engine
Looks like you have to download it from the 3ds homebrew archive section.
Then extract and place the NinjaCam folder in the /3ds/ folder on your SD card.
https://rinnegatamante.it/site/3ds_hbs.php
Edit: Nevermind. I just tried it on my New 3ds. It just freezes with a black screen for me...