Copying items from one room to another can be useful when you need to distribute a single item to multiple rooms at once.
First, make sure you are in the Builder section of one of your projects. Then, click on Edit Items to show the list of additional buttons.
Click on Copy to Room, and you will see an overlay in which you can select the room(s) that you want to copy or move the item to. Once you have selected the rooms, either click Move Items or Copy Items, and that item will be distributed accordingly.