We need to have all configuration that a user can define, which has translatable information on it, to be translatable in the Configuration Translation module's user interface.
There are several pieces of information from the Entity/Field system, which may include translatable strings, but which are not translatable using the Config Translation UI:
a) Field settings. For instance, on a Number field, there are translatable settings for the Prefix and Suffix in the settings config. But if you go to the Translate page for the field, all you can translate is the Label and Help for the field, not the prefix/suffix.
===> This is because the schema is wrong. See. Fields are translatable along with their settings, supposedly anyway.
b) Entity view displays - field formatter settings. For instance, onwe are adding the ability to numbers to have formatPlural() type formatting, but there is no way to translate the "1 item/@count items" strings. These are stored on the entity view display config items.
c) Entity form displays - widget settings. For instance, many text fields have widget options to enter Placeholder text, and obviously this would need to be translated. These are stored on the entity form display config items.
d) Base field overrides, which seem to include labels.
==> will do this on a separate issue
The technical reason is, at least for the entity view/form display formatter/widget settings, that there is not an edit form for these things -- the config schema indicates they should be translatable, but there's no way to edit them so config translation module doesn't put up a UI for translating them either. They are settings that appear as part of the Manage Form or Manage Display pages in Field UI, but the individual fields do not have their own settings forms.
Comment #5 also looked at other config items to see if they were translatable and #8 discussed them; more issues will be open.
Make sure that these items have a translation UI.
Figure out how to make them translatable. Maybe add tests too?
User interface changes
You'll be able to translate your site. Can't now.
Probably not, but we'll have to see what the patch entails.
Data model changes
I wouldn't think so.