You mean like this:
www…com/watch?v=mfbjP_F8-Ko
I tried to do that for a year or so, I was in front of a complexity wall when it came to make multiple sized items.
The solution I found is to simply split the system in two: one part inventory slots, second part items displayed.
I have an inventory of X slots, whenever I drag something hover it I check lots of things and do things based on that.
I’m basically “clipping” item images on the same position than inventory slots.
BUT, this only works in 1920*1080 screen resolution and you can’t single click to start dragging an item, nor can you drop an item hover another and start dragging the new one.
It is basically a “cheap” diablo-like inventory.
But honestly, I had serious troubles getting this implemented, if you don’t have a serious reason to want a multiple sized inventory, you should not go for it.