Hello there, @CMcK1.
Right now, you cannot assign a category to a Bundle in QuickBooks Online (QBO) since these are only used for sales transactions.
To learn more about how Bundle feature work, check out this great resource: Introducing QuickBooks Bundles and Reorder Points.
While we continue to make your experience with us even better, I recommend visiting our QuickBooks Blog to get the recent news, information about the latest features, and updates in QBO.
If there's anything else I can assist you with, feel free to visit the Community again. We are here for you. Have a nice day.