Dear Sir,
First of all, I would like to know whether the required Smart List is a standard GP or built through smart list builder.
In case it is a standard, your choices are limited to the columns provided under the "Add" button since it cannot be modified from the smart list builder.
I do believe that most of the times, GP terms can be misleading a bit as the same instance can be referred to with variance names in various modules or tables. For instance, transaction location. Therefore, please check the columns under the add button thoroughly.
Otherwise, it goes without saying that modifying the SQL view of the Customized Smart list is an easy option.
Best Regards,
Mahmoud AlSaadi