In my editor, used to draw statechart-diagrams, I have nodes (states) and
edges (transitions). Both nodes and edges are equipped with one or more
labels for names, events and so on. In the first stage, a label is only a
text field where the user him/herself can input any information he/she
wants to. Now, I want to change this to a dropdown menu, containing a set
of predefined names to choose from, but I don't know where I'm supposed to
do this. So, my question is; where is the type of the label defined? Where
in the code is it set to be a text field?