It would be really powerful to allow objects to be added to custom UI elements.

What I mean by that is imagine a custom UI with a picture of a bag in it, and if the player clicks and drags off of that UI bag, it would take out the first thing in a certain bag on the table (not at random of course). The idea comes from often having to move the camera around for a few things in games that are just out of view. Drawing a card from your deck, for example, can often mean moving your camera to look at the deck, draw the card, then put the camera back. With this feature, you could put a deck on the UI on the screen which the player could simply draw from like a normal object!

Ideally what would be shown on the Custom UI would be a 3d model of the object itself (like how we see a bag in the Components menu, for example). If not possible, we could just set an image (it would be nice te be able to replace the 3d model by an image as an option even if the 3d model is possible). Another nice feature would be being able to rotate/translate/zoom in on the 3d model of the object in the UI, so we could choose to only show certain parts of it.

Lastly, being able to right-click these UI objects and having the context menu show up would be really powerful. But it would also be nice to be able to turn off that functionality with an attribute.