I understand the importance of being able to insert a line item between existing items on a purchase order in QuickBooks Online (QBO), mauibrakesupply.

With the new interface, the feature to insert a line item between existing items is unavailable. The hand icon is used for dragging existing line items to rearrange them, however, it will not allow for the insertion of a new line item.

While this functionality is not supported in the new experience, users with a Plus or Advanced subscription have the option to switch back to the old layout, where it is possible to insert a line item between existing items. If you wish to switch back to the old experience, you can follow these steps:

1. On the left navigational bar, click the +New button.
2. Select Invoice.
3. On the top-right corner, click the Old layout button.
4. Tap the Switch layout button.
5. Enter or select the necessary details, and then the click Leave and submit button.

If you can't switch between different styles, please send feedback directly to our Product Engineers so they can look into it and add this feature in future updates. Here's how: 

1. Go to the Gear icon at the upper right and select Feedback under Profile.
2. Enter your comments or product suggestions. You can also attach a screenshot or file to combine them all.
3. Click Next.
4. You'll be provided a list of suggested help articles related to your comments. You can read through them or choose Skip and send message.
5. Select the appropriate category from the drop-down menu.
6. Tap Send message.

To learn more about creating purchase orders and sending them to vendors, check out this article: Create and send purchase orders in QuickBooks Online.

Keep your post coming if you need more help with managing your vendor transactions. I'll be around to help you always. Keep safe!