Describe the Suggestion

Make it so that items that already take space on the belt, can be stacked.

Screenshots and Videos

Additional Context

For example in a cobblestone farm, if you have an item of any stack size taking up that space on the belt, it cannot be stacked beyond the point it was placed on the belt at. So if you have a stack of 4 items land on the belt, that stack of 4 goes on the belt and stays a stack size of 4 no matter how much of the same item you try to throw ontop of it.

Have you ever heard of the brass funnel

If you're talking about putting a brass funnel and adjusting the stack size before it goes onto the belt, that's only going to work for some applications. It will also bottleneck because you already set a predetermined stack size and loaded that stack size onto the belt, so if anything on the same line needs to add to it and there's not enough space, it will queue until it has space rather than adding to the existing stack. It will also bottleneck inputs for machines or contraptions if you set the stack size too high as the funnel will buffer to the predetermined stack size until conditions are met.
If you want to make everything overly convoluted with redstone and guestimating crazy algorithms for timing belt speed and length, that's not fun.