In the Inventory search screen [F10] or [Shift] & [F10] search - simply press the letter E or use [F6] options and E to access the Edit Supplier box as shown.
The Low Quantity search will only work for items with Priority / Popularity set for reorder and a Minimum, review Reorder item sent from Inventory under Purchase Order section for details on using this tool.
Enter Supplier Leave empty for all: Enter Supplier Code to search or leave blank to search all items.
By Line Code: Enter the three Character Line Code to search
Along with being a tool to use with purchase orders and order parts this same utility allows for a Low Quantity Report - simply set the filters as outlined earlier then press [F7] print when you have the screen viewing the information desired.