Well, you can draw the STORE widget (not the item) completely, in which case adding it to the viewport makes sense.
But it’s better not to delete EVERYTHING, but only clear the children in the vertical boxes in which the item widgets are located. It makes no sense to re-draw the ENTIRE STORE.
*StoreItems for testing it can be filled manually, but you need to make a separate function for filling the assortment.
You need to remember about optimization and not do anything that you don’t have to do. Creating widgets is not a cheap option.
This should be a store widget function, no need (even harmful) to do it in Game Instance.