I'm not sure if this is by design if I am honest as it seems the functionality is supposed to be this way, but the only argument I have is if there is space in the bag why can't I put it in if an item is 'in the wrong place'? If it was real life, you'd shove that item else where if you needed to do it quickly! I'd expect the inventory system to just be able to re-arrange my bag when I have the space, and then when I don't, it would be good to get a notification! It's just very irritating, because if I need to shoot, and there are zombies around and I say for instance kill someone then these Zombies swarm me and I want to pull a knife after I run out of ammo, I can't? So then I end up getting swarmed by all these zombies (and anyone else) because the functionality just kills me pretty much. It's pretty poor especially as this is in beta.
Apologies if this is not the right category either, but I hope that this can be picked up and resolved, it would make the game so much more enjoyable even with the bugs, if the inventory/actionbar etc would work in sync so I wouldn't have to tab in a middle of a fight and have to drop my gun... Swap to my knife... Then tab out to everyone killing me :(.