The research system is the heart of Journey Mode. When you collect enough of an item, you research it, and that item becomes infinitely duplicable. Common items such as blocks need hundreds, while a single weapon or piece of armor is enough. Everything you research stays available in endless supply in the duplication menu.
Most codes here need cheats turned on first. See the section on how to open the console.
Pick Journey Mode when creating a character
Drop the item into the research slot, and once you reach the required amount it can be duplicated endlessly. The core feature of Journey Mode.
Every item you research sits in this menu in endless supply. Take as many as you want and use them.