I've used
JavaScriptcreator.toolbox.getItemByName("boolean").title = "True / False";
creator.toolbox.getItemByName("boolean").tooltip = "True / False";
to change the name of question type 'boolean' to 'True / False'.
See how it looks in the images below.
But also notice how on the bottom left of the question. It still says 'Boolean'. How can I also change this text to 'True / False'.
Please let me know. Thank you very much!