The phrase
deck:some_function[]
calls a function named "some_function" with no arguments and then assigns the result of calling that function to a variable named "deck". If the result of that function isn't the deck (it appears to be the number "1" in your example), you will then be calling the dialogizer functions with an invalid "deck" argument, which prevents them from working correctly.
If you have defined a function in a deck-level script:
on some_function argument do argument+2 end
You can invoke it from any card- or widget- level script by calling it like any other function:
some_function[3]
Widget scripts exist in a scope nested inside card scripts, which in turn exist in a scope nested inside the deck level script which in turn is nested inside a special magical scope with the definitions of all the default event handlers. Every variable or function definition in an outer scope is visible to the scopes nested within it, unless one of those scopes "shadows" it with a local definition with the same name.
Widgets, Cards, and the Deck all expose a ".event" attribute which is a function you can call to send a synthetic event to that deck-part. You can thus also invoke that deck-level function from elsewhere like so:
deck.event["some_function" 3]
This latter method works even if the target is not in a scope surrounding the caller, and it sets up automatic variable bindings ("me", the widgets on a card by name, etc) from the perspective of the target. This is most useful when you want to communicate across cards or simulate user interaction, like sending a button widget a "click" event which appears from that button's perspective like a user-generated click.
Does that help clarify?