Spring RTS Engine

does anyone know how to bind the "\" key (left of Z on keyboard) to a combination of pressing shift + alt

It would let me press 1 key to drag a box instead of shift + alt

I tried adding "bind \ shift+alt", to bind widget but it didn't work, when i press it it always draws on the map instead

I am not sure you can bind a key to a modifier.
You can bind keys to actions, and one of these actions can be "fakemeta", which allows you to bind any key to the "meta" modifier. Other than this particular one, i don't think it is possible.
Also, "/" is not a modifier, so you won't be able to bind ie "/+key" either.
What you might be able to do though, is to bind "/,key" ("/" then "key") to your action. I believe keychains should work, but I am not sure it will help you.

You could always make use of a widget for that though. It shouldn't be all complicated.

shift+alt or alt in general is also a bit a problem to me cause sometimes it turns my map. is it possible to move that freecam mode to another button and if yes how?