This is a HOW TO, not a question :-)

Binding numeric keys (for example KP_1 or KP_0) is not as easy as it might seem. A simple bindsym $mod+KP_1 does NOT work in X11 (but maybe it works in Wayland?).

Solution

for example to define a key binding to switch to workspace 1 we can use: bindsym $mod+Mod2+KP_1 workspace number $ws1

Background info: Mod2 specifies the numlock key (although xev reports it’s called Num_Lock with code 77). Mod2 is not a key to be pressed, it seems to be the numlock state, so +Mod2 means the keybinding is active with num_lock enabled.