In my view these flowchart systems look like they work well for simple cases, but for more complex cases you end up with a pile of spaghetti and endless scrolling which makes it hard to even find anything. I doubt it would be easy to track dialogue in this type of system if you had a novel-sized amount of content (e.g. 300+ pages, 80,000 words). You'd have a huge scroll distance and everything scattered over an enormous area with incredibly long lines joining tiny fragments of text.
For more complex cases a linearly-written approach may work better, with the branching done conceptually. The way event blocks work is analogous. Events, conditions, actions, functions etc. all conceptually branch and could be represented as a flowchart system. However keeping it in a single list actually makes it much easier to work with when you end up with a large number of events. I think a data-driven approach like JSON is the equivalent for managing large, complex trees of dialogue. However I do appreciate that takes more work to set up and involves learning more like how JSON works. But it may well be worth it in the long run.