! Mod is now redundant, the base game UI is made compact for interaction and with new textures !
Initial problem with inventory was that there is a grid between slots that doesn't let you drop items into, or pick them up. In short - a non-interactible void zone. What if you could expand the slots all directions so that they cover the void zone, but still show the grid? That's what this mod does. The side-effect was that i had to alter recipes and tabs graphics as well because they are tied to same spacing system. And while at it, i decided to use the new 0.17 UI graphics! I worked with Gimp to recolor tiles and everything because i cannot simply use the gui-new.png as is because of needed spacing, and inventory colored graphics did not yet exist.
Another just discovered (good) side-effect of this mod was that all other UI's (assemblers, miners, power graphs, module slots) now use new graphics.
But overall this is very lightweight and non-intrusive mod you can uninstall at will if it's not to your liking. Let me know in comments if something still needs adjusting and i'll see what can be done. Ideally this mod should become deprecated when the new UI changes by Factorio devs fixes all this, but for now that is unknown.
If anything, now you have a modding resource to alter the UI to your liking.