It is possible to swap weapons in keyboard mode:
Hold "Ctrl" + "Shift" + (equipped item)
Hold "Ctrl" + "Shift" + (item from inventory)
I couldn't find it in the instructions, but that's worked for me.
It's under the advanced commands, on the parts window (all commands are shown on their relevant windows when the mode is activated).
If you are trying to use keyboard more, make sure you read all the advanced commands! You can do literally everything by keyboard, and it's really fun and fast
You can already do swaps by holding shift when you drag the items around. But maybe it really should be the default behavior...
Yeah, that totally should be a thing. Equip or unequip if the item is dragged onto the window in general or onto an unmatching item, but swap if you drag it on a matching, swappable item.
Make the target item glow in some special way when you drag over it if it would be swapped and replaced by the item you're dragging.
That's an interesting way to look at it. It wasn't the default behavior because I wanted players to be able to just drag items up and down without regard for where they were dropping them, and let the game figure it out. But mouse users do need a slightly quicker more reliable way to swap items like keyboard users have, and as you say, the UI can do the type differentiation for you and even glow a bit to show that a swap will take place.
The only problem I can see is that players don't often realize that you can drop the item anywhere, and try to put it directly into an empty slot--this could mean they might accidentally swap with an item adjacent to an empty slot rather than attaching. But I guess gamers' mouse accuracy is pretty good in most cases...
That change will definitely be going in!
I wish Dwarf Fortress had an interface as sexy as this one 
Hahaha 
I hear ya!
Me too! That is such an awesome game, but I couldn't get into it because the interface is such a chore that I always felt like I was wasting too much time.
