With Suggested Item, you can define items that could be sold along with the main item. For example, my company sells laptops but sales persons also suggests other items like Mouse, Keyboard, Printer, Hard Drive etc.
Suggested Items are available in Item Maintenance window, Setup the item and Click Suggest Items.
Suggested Item, windows shall be available within SOP transaction, window will automatically appear when Item having Suggested Items where selected on the line item,
Alternatively window can also be opened from the Options Menu of the SOP Transaction, make sure line item is selected.
SOP Transaction line item will have suggested order along with main item
There is no flag in printing, whether item was main item or suggested item, for example if you have if you need to send quotation of main items and suggestions separately you may need to customize your quotations.