Pressing the U key on the item first shows all synthesizable items, from which we then select to view the item recipe.
When the game has a large number of recipes, pressing the U key on an item, jei show all the synthesizable items for that item, and there are hundreds of pages or more to find out what it can synthesize. I think before that, it should show all synthesizable items in a slidable page. We look for items to synthesize from this page.