If you are stuck, do not look for codes. Instead, focus your gems on purchasing Hearts (Health upgrades) and the Flame Wand . These two purchases essentially act as a difficulty slider.
Shovel Knight Dig uses a "Feats" system (called Wandering Traveller) that functions similarly to cheats or modifiers. shovel knight dig cheats
While there are no code inputs, you can unlock items that significantly lower the game's difficulty. If you are stuck, do not look for codes