There's no customization available for Ignition's built-in error popup, AFAIK. I recall scripts posted here on the forum to auto-close the popups, but I haven't used them. You can improve the behavior of scripts with consistent use of jython try ... except ... clauses, catching errors before they get to the built-in popup. Do note that jython needs two except clauses to catch both jython and java errors, like so: