Only with a custom program.  It's not how Sage 300 is built.

You should be able to sort by item number in the Crystal report if this is what you are looking for.

Because the item is a key field in the detail data, you cannot.  If this became a hard requirement, you could create a macro to:
1. Read / sort the data
2. Write to a new order in desired order
3. Delete the original order

What problem are you trying to solve by sorting by item?  If it's to print the order or picking list by Item#, that can be done in Crystal Reports as suggested here.  If it's to find items on a very long order during shipping, have a look at Tairox Productivity Tools, on the "Ship" button.  That still shows items in the order they appear in OE, but allows you to easily find by item and enter quantities on the selected lines.  If you need that window sorted by item, it's possible that Tairox would be able to add it for a fee.  Otherwise, you have to do some custom programming.

Thumbs up for Tiarox