GUI Accessory-like system

Hello community! I am making a simple accessory system for my mod and what I want to achieve is that by pressing a certain key, the interface to place the accessories opens. So far I have managed to do this, pressing the "M" key opens the interface without problems and allows me to place the items (in this case, accessories), but when it is closed the items are removed from the interface and fall to the ground. Is there a way to make an interface that can contain items but is not linked to an inventory block? I am currently developing my mod in version 1.12.2, and I don't know if it is possible to do something like this, but thank you very much for the help.