Thanks for joining the Community, alex187.
I can certainly understand how an ability to close multiple purchase orders at a time could be useful and have submitted a suggestion about it as of today.
You can also submit your own feature requests while signed in.
Here's how:
- Use the Gear () icon, then go to Feedback.
- Enter your suggestion(s) in the Have feedback? window.
- If necessary, attach a file with your Camera () icon.
- Select Next.

Your feedback's definitely valuable to Intuit. It will be reviewed by our Product Development team and considered in future updates. You can stay up-to-date with the latest news about your product by reviewing Intuit's Product Updates webpage.
You also have the option of checking our QuickBooks App Store for apps which may be able to help you achieve what you're looking to accomplish.
For the time being, purchase orders can be closed individually while you're editing them. You'll need to switch their statuses to Closed, then save your changes.

If there's any additional questions, I'm just a post away. Have a wonderful day!