Need assistance combining 2 items?

Hi Modders I find myself in a pickle as i am trying to combine two items lets say a wall and a storage box into one item. My item is there, but i can’t get it to show on my engrams and inventory… I am still a newbie into modding and would really like to get my mod going. I had it where i was able to place it on a foundation but once placed it disappears… any help will be great thanks in advance…

Id say watch this video

Thanks will have a look