Hmmm, it only took a few years since it was first requested and still it's not perfect. Sure, it shows the various modifiers and whatnot but even those are not complete. It won't be showing casting modifiers and it most certainly won't be showing damages of any kind. The functions that calculate them are 'UGE and in order to print out a simple 'Main Hand Damage: 2-7', as is the case here, it would require a shitload of code and I'm lazy.
Anyway, I'm sure some players can tell exactly what stats the rogue in the image has and what changes there would be if he removed the shield, but I'll list them anyway: (STR 8, AGI 6)
Main Hand Damage Modifier: 1 --> 2
Block Modifier: 1 / 2 --> 0 / 0
Parry Modifier: 0 / 0 --> 0 / 2
Deflect Modifier: 1 --> 0
As I said, I'm lazy, and that means that there won't be any fancy button to toggle that screen and you'll have to press Ctrl (or whatever you bind on the Use button in the options) when the inventory is visible to show it (whenever the next version comes out that is).