I admit I've been bouncing around addons when it comes to trying to find the 'perfect' solution to what I wanted with dialogue trees and initially thought I had one but it didn't really offer proper options for interacting with variables etc. in the editor as well as accessing these same variables within a script within the game engine. I think that's because either some of these addons were strictly developed for a visual novel or the people making these videos simply didn't know how to do it and were just pumping out a video for the sake of it.
Luckily I came across a not so out of date video on dialogic and it looks like the addon isn't abandoned either and is getting updates.
https://github.com/dialogic-godot/dialogic/releases
https://www.youtube.com/watch?v=7PuPU0Mrl_g
There's a little bit of quirkiness as one would expect from a new alpha when installing the addon to the game engine but other than that I don't understand how they haven't put Dialogic in as a full contribution.
It's absolutely fucking amazing, you've got access to a full dialogue tree. You can do tons of choices, conditions based on a variable you have and you can even connect signals between it all within this quite neat and colour coded UI. Even better, there's sound and things like that, if you wanted to, you could do a full visual novel with this easy.
I am getting tons of ideas I would have thought would be potentially quite difficult to implement due to the fact that coding your own solution to this would be an utter bastard. I may even ask the Godot devs themselves why they haven't found some way to integrate this into an official version because I think it's that good.
With regards to dialogue trees generally, I've been only experimenting a bit because I've been so busy, but it's made me feel like I'm a modder rather than a game dev in this particular aspect which means of course it's going to be dead easy to churn out story elements for any games.
I can see so many use cases for this addon it's insane.
When you look at the other options you'll realise why I'm perfectly happy with this one lol some of them do have a node setup if that's more to your preference but they have their own issues like incomplete documentation or poor explanation. Or alternatively accessing variables between the dialogue editor and the scripts is a massive pain in the arse.
Now I can have exactly what I need for proper quest interaction and dialogue, so for example I can have the usual RPG setup with stats and currency among other things. Then I can have the same variables within the editor updated if there's ever a change if necessary, can't do that in the other addons quite so easily.
That example you looked up I get where you're coming from but it seemed too limited for my tastes.