The tips are ordered by the progression through the game.
When trying to calculate how much electricity a certain amount of fuel would generate, there is no consumption recipe in the list that would take this fuel and convert it into the electirity. That's because the electricity recipe is special, so you need to add it by either clicking on the Electricity icon and selecting the sole production recipe there is, or through the dropdown menu on the top left: Recipe > Add Recipe > Electricity.
Sometimes it's more convenient to set up ore expenditure rather than the amount of the final product. You can do it by putting the ore into Desired Products and assigning it a negative number.
Do you want to produce a Used-up MOX Fuel, but there is no production recipe?
Select the recipe to consume the MOX Fuel, and look at the Summary Ingredients and Extra Products - there should be the Used-up MOX Fuel. You can link it, and Yafc will balance things out as usual.