In case you have a lot of campaigns, it is very useful to have an option to separate them into some groups. The 'Campaigns categories' feature enables you to do this. First, you have to activate the feature in the merchant panel at Configuration > Features.
Then navigate to Campaigns > Campaigns categories and create as many categories as you need. Click the New Category button (1), then click the new item (2) and modify it in right panel (3).
Do not forget to save your changes. In our example, I created 3 main categories and 2 subcategories (you can create it by clicking the main category and then the new category button).
Now, we want to insert one of the campaigns into the category. Navigate to Campaigns > Campaign manager and edit a campaign. In the Overview tab, scroll to the bottom and click the link Change. Choose the category and save.
Your affiliates will see it like this (in affiliate panel):