Users accustomed to the classic print experience with individual Print Preview, Page Setup, and Print elements have clamored for a way to bypass the new combined Preview/Setup print experience. But now that they have it, there isn't any GUI to modify print job parameters such as scaling and whether to print headers/footers.
It would be useful if the
tabs.printPreview() API call could trigger the combined Preview/Setup print experience regardless of the value of
print.prefer_system_dialog to work around this issue so that users won't need to manually modify preferences in
about:config as often.