You could simply create an action (for example using an action node aka script node, or an on-entry / on-exit action on nodes that behave as a wait state), and then use either mvel or java syntax to set your map (example uses Java syntax):
java.util.Map map = new java.util.HashMap();
map.put("variable1", ...);
...
kcontext.setVariable("myMap", map);
Then just map the myMap variable to the Content parameter.
Kris