If even after adding chrome folder thuderbird doesn’t use your cutomized css, you should try with:
Settings/Options > Advanced > General > Config Editor
toolkit.legacyUserProfileCustomizations.stylesheets > true
a thoughtful use of digital
If even after adding chrome folder thuderbird doesn’t use your cutomized css, you should try with:
Settings/Options > Advanced > General > Config Editor
toolkit.legacyUserProfileCustomizations.stylesheets > true