Create a Text & Image object. For the text enter:
This will display the value of a default variable that is created by the editor. You can reference any other variable that you create in a script in the same manner, using any other object.
If you are looking for displaying all variables from a script, not sure if there is a trick to do this quickly, without resorting to some fancy scripting (to put name/value pairs in a table for display in a table object). But if you have a few variables you want to keep on eye on, you can string them together
='Var1: ' & Var1 & 'Var2:' & Var2 ....
If you are debugging, check out the debugger in the data load editor, this shows you the values for each variable as the you are stepping through your script.
Hope this helps.