Vertical formulas can take a bit getting used to. Simple formulas can be easier to understand if they are written horizontally. However, the more complex a formula is, the more I find that writing them vertically is necessary for me to keep track of all the pieces.
Plus, there are multiple ways of writing things vertically. For example, some people write an
if statement with the condition on the same line as the
Just use whatever method works for you. I only suggested this method because you mentioned getting lost in nested if statements.
I write simple (one line) formulas directly in the Airtable editor. I write short, multi-line formulas in whatever text editor I have handy (often the very basic Notepad that comes with Windows because it opens quickly). I write long, complex formulas in the free code editor Atom, but any code editor would work.