How to edit a packing slip in QB online? Has this issue been corrected in QB Online?

It's a pleasure to have you here today, @NC Questions.

Since customizing or editing packing slips isn't available inside QuickBooks Online (QBO), we recommend sending a feature request to our Product Development Team. This way, suggestions reach our engineers, and they'll evaluate the idea and consider it for future updates. We'll write down the steps to get you going:

1. Access your QuickBooks Online company.
2. On the top right-corner, click the Gear icon.
3. Select Feedback and then enter your comments or product suggestions.
4. Once ready, click Next to submit feedback.

On the other hand, the option to modify packing slip in QuickBooks Desktop (QBDT) is still functioning as designed. For more details, please see this page: Use and customize form templates.

In addition, here's an article to help you create personalize sales forms inside QBO: Customize invoices, estimates, and sales receipts in QuickBooks Online.

If you have other concerns about packing slips or sales form templates, don't hesitate to visit the Community space anytime. As always, we'll be around to help you out again. Keep safe. 

To answer your question, the answer is no. The customization of basically all of QuickBooks online is non existent. People have been requesting this change for at least 5 years now and nothing has been done. 

Sad….. this program could really be good with a few simple changes. 

Exactly! Well said. Really not sure what their problem is. But ignoring their customer base is NEVER a good business model.