easiest way to do this is to make a slot array so after u add a slot also add it to the array. also add a isfull bool to your slot widget. this way any time u add a item to it u can also set the isfull bool to it also suggest adding ur item struct info to it as well for checking item ,item type ect for more complex stuff. so then when u need to check to add a item to it u can just do a foreach loop with break check to see if the slot is full if it is ignore it or what ever u need to do and if its not full u can add a new item to it and then break out of the loop.