Set up your spreadsheet
To add multiple categories, you just insert new lines in the category fields to add additional categories. The key is though that they must line up and the deepest categories must go first - e.g. if the first one is 2 subcategories deep, the second one is 3 deep then the second one with 3 categories deep one must go first & so on.
Note that pressing Alt + Enter allows you to add a new line in the same cell.
It is important Categories are ordered correctly. Changing the order will result in a bad import and unintended categories. The system will ignore the empty lines and align the fields. In this example. We ended up with a category named Sale/ Active Wear