I use CyanogenMod 11 M12 (Android 4.4) on my own device, and I can’t confirm that the icon is too far on the left.
I think I won’t ever be able to make a a single GUI dialog that works on all Android versions. Maybe there’s an experienced Android developer somewhere who can help?
@ragged by the way: “And it would be very useful to be able to change the calendar after adding it.” This would be a feature of the calendar app, not of the sync adapter.
