This mod shows an additional information panel in the crafter’s workshop to display the number of items you already have (in stock and deployed) for the currently selected crafting recipe.
Heads up: tracking items like that is super expensive, and makes the JS garbage collector very, very sad (to the point of eventually killing the whole UI). That fetches the JSON for every item from the C++ client to the JS process whenever anything in the inventory updates. A bunch of our code was doing that in the past, so sorry for setting a bad example - it’s been fixed since. You should be able to access anything you need from those items using App.catalog.