Yes, you can manually select a retailer by dropping a pin on a map. To do this, Edit a shopping list and tap on "Tap to pick location". Tap on the Map button on the top right corner of the screen. This will bring up a map showing a region around you. you can pinch to zoom in/zoom out on the map to look for the retailer location and once you find the location, tap on hold on the screen location for 2-3 seconds till a pin is dropped. Now tap on that pin to see the address and select the address to save.