Hi Charly,
Recently I have implemented a quite similar constellation. I have 2 customer-exit variables ready for input where I propose default value (i_step = 1) on the variable pop-up. The user can overwrite it.
Another customer-exit variable not input-ready (i_step = 2) will use those 2 variables.
In any case (either the user accepts the default value or overwrites it) the variables are available in i_t_var_range. Please believe me that this scenario must work.
Please share more details of your configuration of the customer-exit variables (e.g. screenshots) and the respective coding of each customer-exit variable. Maybe we can then identify what is going wrong.
Thanks,
Sander