Can I remove the product categories from showing up in my purchase orders?

Welcome to the Community, cksabal.

Taking out the product categories from your purchase order is unavailable in QuickBooks Online (QBO).

QBO will display the product categories if you use the Category details section to enter your transaction that directly affects the account. Thus, removing them from the form is unobtainable. 

On the other hand, you can use the Item details to track the transactions by item. This also refers to adding an item by quantity and unit price.

To understand more about how to view your best sellers, what's available, the cost of goods, and other topics, feel free to read this article: Use reports to see your sales and inventory status.

Don’t hesitate to comment on this thread if you have more questions about purchase orders. I’m always here to help.