While KM does a good job of handling simple dictionaries, it is not well suited for complex array of dictionaries. JXA can do this much better, and much easier.
I'd suggest that you discuss the complete scope of your task/project, and then we can suggest some good choices for implementing it.
They are automatically deleted because they are "Local" Variables , and as a result are NOT in the KM Variables list.
Yes.
It is not as well structured as KM Variables, you can see them in your token: KM Editor menu Edit > Insert Tokens > Dictionary.
Anywhere you have an Action that accepts text/tokens, you can insert a Dictionary token to display the value for key.