when making a hotstring, you must keep the same hotstring, and just vary the key pressed.

so, on wow1 the key would be '1' and the string might be 'attack.1'
on wow2, the key would be '3' and the string would still be 'attack.1'

so on and so forth

if you have a wow that doesn't have an action for that hotstring, just leave it off that wow and no key will be sent to that wow