In Chapter 6 of The Mandalorian, sharpshooter crew member Mayfeld uses an additional blaster that extends from a pack on his back, but, from I saw there's no nerve connection from the pack to his body and he didn't press any button or make a specific gesture to initiate or shoot it.
How exactly is this additional blaster operated? How does it know when to shoot?
In Star Wars Gadgets and Gear sourcebook there are many backpack-mounted types of weapons, from Laser Rifles to Grenade Launchers that are operated via cybernetic commands by the character. The Blaster from Mayfeld's back is most likely a similar type of backpack-mounted weapon.
As to how it works, the Blaster arm is probably attached to a semi-autonomous body inside the backpack (like how the J-1 semi-autonomous proton cannon works).
This is the best explanation I could find.
