This mod adds a small number to the screen to show how many of the item you're holding you have.
I quickly whipped it up to do what was requested here: Count all items in inventory when an item is in hand
It will most likely work on older versions. I have tested it on 0.11.13 and was able to load a multiplayer savegame using it. I have not tested for desyncs.
Example:
I have 50 belts in my quickbar and 130 in my inventory. I grab the belts from my quickbar and this number appears:
![Image](https://forums.factorio.com/images/ext/7638152e3b7713e792f2584a878c2142.png)
Enjoy.