I have not fully completed the user-input system; I still have to add the functionality to grab variables from generators within generators within generators, etc., but the useage of user-input variables and the setting of them is completed, so I have uploaded that part to Enworld.
To add a custom user-input variable, start creating a generator, then click the "Add A User-Input Varibale" link. This will make some forms appear.
The "Name" form will change how you refer to the variable in the generator. For instance, if you entered "gender" into the name form, you would refer to the variable in the generator with "{print:$gender}" or "{if:$gender=male}" etc. The "Name" form will also be the title of the variable when it's displayed on the view_block page.
Each "Option" form will change what the variable's value will be. For instance, if you made a variable named "gender" and gave it the options "male" and "female," {print:$gender} would either output "male" or "female' depending on which is selected by the user.
The "Add Option" link will add another option to the variable it is in. You must have at least two options for each variable. The page won't let you submit if you don't.
Clicking the "Preview" link inside each user-input variable will change the forms into a select box, so you can preview how the generator will output with the different options. After you clicked the "preview" link inside a variable, it will change into an edit link, which will let you edit the options and add/delete options again.
If you don't click the preview button inside a variable, it will output as "Variable Value" when you previewing the generator.
After you've submitted or edited a generator with custom user-inputs, each variable will appear as a select box for the user to choose from in the view_block page.
Please let me know if it works correctly for you or if you have any questions about the functionality.
I'll probably be done with the rest of the user-input functionality pretty soon.