EvandroCapo Hey, thanks so much! I'm really glad you like RPG in a Box! 😄

I'm not sure I completely follow regarding the codex question, as the script you included seems to work properly and correctly accesses the codex by key. However, in this particular case, there is a bit of simplifying that could be done (assuming that the only purpose of the codex is to find the matching lowercase name to display in the dialogue). The first variable could be an array instead of a codex, and then you could use $result directly to find the matching name in the array by numerical index:

$choiceToItemName = array["strawberry", "corn", "potato"];
$choices = array["Strawberry", "Corn", "Potato"];
$result = display_choices("What do you want to plant?", $choices, entity["npc_id"]);
display_message("You dont have " + str($choiceToItemName[$result]) + "!"); // strawberry / corn / potato

Regarding uppercase and lowercase, there aren't currently functions to convert strings between uppercase and lowercase, but it's definitely something I plan to add. Let me know if that helps!