What is an example of a nonessential ingredient in a recipe?

This is how I'd decide what the answer is:

1. Something with very little taste, esp. in smaller amounts, like dried parsley.

2. Sometimes I think chopped nuts would be another example in recipes like brownies due to personal taste or due to Allergies or maybe the type of nuts used (I like pecans better than walnuts, for example and my mom prefers dried currents over raisins in baked goods). But not if it's a recipe for Nut Loaf or something like that.

3. Or something added in to a particular recipe version to give it an signature, ethnic, or texture "twist" like water chestnuts in turkey stuffing.

When I'm cooking and missing an ingredient or know it will be disliked with a certain ingredient, I pick and choose some ingredients based on preference, availability, or more benign flavor or texture, like dried parsely. But a chef might toss me out of the kitchen for that. Essential ingredients, to me, are the ones that you need to make it taste right, have the right texture, or cause the right chemical reactions needed to create the finished product. Leaving out things like eggs, milk, butter/fat, flour, baking powder, soda, or even cream of tarter (or its baking soda & powder equivalent) is a bad idea. If you're making something you don't eat or haven't tried before, sticking to the recipe is more important--I think. I don't eat blackened chicken, but my ex husband does, and after several different recipes and my own modifications based on how it smelled and lookef at his favorite restaurant and what he told me it tasted like to him, I finally got it right according to what his grandma made and how he likex it. So now I don't alter my spice mixture amounts at all. I can't taste it because it's way too spicy-hit for me. So I have to think of each ingredient and its amount as being essential.

I might have the wrong answer here, but it's based on a lot of goof ups in the kitchen and many preference and successful copycat attempts like trying to recreate 'grandma's spice cookie/honig kuchen' (still don't have it exactly right) or the 'knodel I had in Austria in like, 1972'.

(Sorry it's so long. iPod typing in boxes is hard to gauge length for me--I don't know how to scroll up.)