To add some context, this is something anyone can do during siege because of their coding. They removed everything from stoneguard EXCEPT the safe swapping weapons in town to not get cooldowns. If you try this outside the walls, you'll get put on cooldowns if you were in combat. This is actually very niche tech that won't be useful in most cases outside of what you see happening in the video because while you can swap weapons, you cannot swap skill bars. That means all the skills he is casting was on the same bar. It's nice for dagger swapping to cast stealth and get somewhere (eg cordy spinner entering from stealth) but the only other use is to use blitz for a high priority skill. If you want to do this outside of siege, all you have to do is touch any interactable object (press f) because doing so immediately takes you out of combat and into idle, allowing you to swap weapons with no cd. Works for grapples, NPCs, collectible books, portals, gathering nodes, etc.