Here’s an example script that uses a “bool” modal:
petting:alert["Do you want to pet the bunny?" "bool" "Pet"]
if petting
alert["The bunny basks in your affection."]
else
alert["The bunny wanders off, looking for carrots."]
end
The documentation says “Prompt the user with two buttons, “Cancel” and a verb given by x (or "OK", by default).” so I’m pretty sure you can’t change the “Cancel” text.
If you want the player to choose between options with no “I clicked the wrong button, get me out” option, like in a visual novel, you might be interested in the Dialogizer library, which lets you show visual-novel style dialog boxes, including choices.