As part of the support for categories (T188605), translators may find convenient to add more categories to the page they are translated (beyond those added automatically from the source article, T177303).
To support this, an "Add categories" input is provided as part of the list of categories in the translation. The input will provide a list of relevant categories as the user types. In this way, users can type the name of a category and insert it to the list.
The functionality should be the same as the input from the Category panel in Visual editor shown below:
In this case, the autocomplete options will include initially as suggestions categories based on the source article. That is, if there is a category in the source article, for which an equivalent category exist in the target language but it is not included in the translation, it will be suggested.