You can now bulk tag/categorize existing content.
You can either add new tags to a content item or replace the existing tags.
To do so, navigate to your Content Library and hover over the gear icon. From the expanded menu, click "Bulk Operations".
Choose "Re-Categorize Content"
Select the content you want to categorize and choose the categories to tag the content with. Optionally, select if you'd like to remove the existing tags on that content.
Click "Add Categories" when you're done. The categorizing will happen asynchronously in the background so you can work on other tasks or even close the window.