This is one of those areas I think Alexa does fine with... I have a difficult time seeing where you need another Skill to muddy the waters.
I didn't even recognize the OP had a Skill for this in use, until I read the last couple of comments... Alexa Lists are Awesome and save the items on the list to re-use later... my wife and I go through the list of items we have put on the list previously, to help us decide what we need each week before we go to the store, and also add and remove items by voice if we don't remember whether the item is on the previous lists... On my Phone (and my wife's) in the Alexa app, we just click on the menu stripes , upper left corner for iPhone, and then from that menu, choose lists. After that when you choose the list you want to see, it shows the currently chosen items at the top (Not in any specific order I don't think), and at the bottom of THAT list, the items that have been put on the list before and have been checked off, are also there, in darker print with an open circle next to them to allow you to re-use that item on the current list. Make a practice list and it becomes clear when you use it how things work. Pretty easy to go through the store and check off items as you shop as well.