how can I create a custom food for a Wendy's single patty with cheese ( no bun, no toppings...) ?
Unfortunately, you cannot alter ingredients in set restaurant foods that are in the system already. You will have to just build your own personal recipe where you build your other recipes. Then add the ingredients, i.e., cooked ground beef (not lean, I assure you), then everything else you add to it. Label it "Wendy's Burger" and then pull it up each time you eat it that way. Now, the great thing is, if it changes each time you eat it, you can R-click over it when you put it in your log and select "explode recipe". It then brings up the ingredients individually and you can change the amount to make it for what you ate that day. This is great for smoothies or omelets, whatever you eat frequently Hope this helps.
That's true, if you are skipping the topics, there is not much to do unless wendy publish the nutrition of a patty.
but if you were keeping the topics, you could make a recipe that was
+1 Wendy Cheeseburger
-1 Wendy Premium Bun.
that would subtract the the bun from the burger - but would still include ketchup etc