[JimmXinu]

Found a couple more problems:

Adding a new named setting fails:

Spoiler:

calibre, version 0.8.49
ERROR: Unhandled exception: <b>NameError</b>:global name 'settings' is not defined

Traceback (most recent call last):
  File "calibre_plugins.generate_cover.dialogs", line 379, in add_setting
NameError: global name 'settings' is not defined

GC doesn't handle a configured font being removed well:

Spoiler:

calibre, version 0.8.49
ERROR: Unhandled exception: <b>IndexError</b>:list index out of range

Traceback (most recent call last):
  File "calibre_plugins.generate_cover.action", line 53, in _generate_cover
  File "calibre_plugins.generate_cover.dialogs", line 1125, in __init__
  File "calibre_plugins.generate_cover.dialogs", line 1315, in display_preview
  File "calibre_plugins.generate_cover.draw", line 232, in generate_cover_for_book
  File "calibre_plugins.generate_cover.draw", line 44, in get_textline
  File "calibre_plugins.generate_cover.draw", line 38, in get_font_or_default
IndexError: list index out of range

Unsurprisingly, importing a setting with a font that isn't installed does the same thing when you try to use it. Maybe check fonts on import, and report missing ones while changing to default?

While not necessarily a problem, I'd expect it to ask if I wanted to save unsaved changes before exporting a setting.

Jim