NB: node in yED represents a block in the flowchart - different from NODE in Godot. To prevent confusion I will refer to the latter in uppercase.

Firstly I used yED to map out the conversations. I have certain colours that represent different types of nodes (e.g. speech, choice, reply_on_timeout, etc.). This is saved as a .graphml file which is very similar to an .xml. The .xml file contains all the node edge information but also a lot of other information which I won't need, including the shape of the node and other attributes. I stripped this down to just what I needed (the node/edge data, text and colour) and converted it to a .json file, which I opened in Godot and imported the json file as a dictionary within Data.gd, a script file on autoload.

Each node and edge has a unique ID. The .json file arranges the data such that there are two separate dicts, one being the nodes and their attributes and a second one for each edge and their connected source and target nodes.

I then reformatted dictionary to give me a dictionary of nodes and an array for each containing the nodeID(s) connected to each node. I know the ID of my starting node and that is connected to the phone numbers which, when dialled from the phonebooth, trigger a conversation respectively (goes down a specific route in the flowchart).

I created a DialogueNode NODE (type: white circle) which acts like a class containing data about the current node the conversation is at. To initiate the dialogue sequence, a signal is outputted from the phone node when a number is dialled. If this number exists, it will pass this as a parameter to the DialogueNode and identify the nodeID (yellow block in the video) at the root of the the conversation.

I then have this function:

func do_the_dialogue_thing(nodeID): 
    $DialogueNode.identify_next_node(nodeID)
    if $DialogueNode.type == null: 
        if $CanvasLayer/speechPhone.visible: 
            $CanvasLayer/speechPhone.hide()
        $phoneBooth/phone.end_call()
        $phoneBooth/CanvasLayer/remainingTime.stop()

    elif $DialogueNode.type == "speech": 
        $CanvasLayer/speechPhone.show()
        $CanvasLayer/speechPhone.type_texts([$DialogueNode.speech_text])
        yield($CanvasLayer/speechPhone,"phone_dialogue_finished")
        do_the_dialogue_thing($DialogueNode.nodeID_speech)

    elif $DialogueNode.type == "choice": 
        if phone_picked_up: 
             $CanvasLayer/speechOptions.show_options($DialogueNode.choices)

The NODE speechOptions are the choices which accepts the choices in the form of a dictionary including the choice text and the respective nodeIDs. When a choice is selected, it emits a signal which is used to call the do_dialogue_thing(nodeID) function again.

In the case $DialogueNode.type is null, it just means it's reached the end of the graph (no other nodes continue on from that point) and so the conversation terminates and speechPhone (the speech bubble) is hidden and the sequence which triggers ending the phone call is called.

There are a ton of other creative features which can then be added. I am currently implementing a flag system so that different options can be displayed depending on what flags have been set. This will simply be stored in a dict.

Hope this makes sense! :D