Disclaimer that years ago, I was impressed at how slick the TurboTax website was.
So I'm surprised they even still have a desktop version (...presumably not just some electron wrapper). And given how it works, I'd guess most of your data isn't staying local for much of this.
Their website is pretty garbage IMO. Every single click is a spinner image for 1 second while the layout adjusts and fetches data. I’m not certain if this is a react or vue or whatever FE JavaScript thing but it’s extremely prevalent across the web and pretty much completely defeats the purpose of having a SPA design.