During a generator run a string can be prompted from the user by using the Ask template:

prompt 'Enter a string' ask

This shows the user a dialog with the specified prompt text. The text the user enters is then output to the generator output, useful for example to name generated files. If the user cancels the dialog, he is given the choice to abort the generation.

A variant of this command, prompt...askFilename, will request a filename from the user with a file dialog.