The target categories the translator added or adapted from source and decided to keep for publishing are never saved in backend database. So when a translation is restored, these edits in target categories are lost. This was not a big problem in CX1 since it was only automatic adaptation of categories and no feature to add/edit categories.
In CX2, if not immediately, we will have these features and there should be a way to keep them between translation sessions. We can consider this as a metadata of an article to publish.
 Decide and design the new table for saving this information. Consider if there are usecases that we can merge with this and make the table more generic?
 Develop the API, PHP classes to use the new table
 Translation restore should fetch this data
 Publishing should use the categories
 Any edits in the categories collection should get auto saved just like any other translation section