To mark items as bought? When you are in the store, just swipe right on the current grocery list to mark items as bought.
Alternatively, open the item and tap the Bought button on the item details page.
The app “auto cleans” bought items on the list. Just mark stuff as bought, don’t delete items.
It shows the last bought item in order to facilitate undo – just swipe item again to undo the purchase.
The undo item is hidden some minutes after it was bought.
Once you buy another item, that one becomes the “undo item” – but you can still see all bought items on the history tab of the shopping list.
The next time you go shopping, no “bought” markings will be left in the app – and you start with a fresh list of things to buy.
The reason Grosh removes bought items is to make to declutter the display of the current list. It makes the list shorter and shorter as you work your way down through the list.
PS. If you added an item to the list by mistake and you are not going to buy it, swipe left in stead and tap the “Delete” button that appears.