[] keys - where?

Unless you are using a non-English keyboard they are to the right of the 'P' key - [ and ] unshifted, and { and } shifted. This is the case even on my Windows keyboard, and folding keyboard for Palm.

They should be accessible this way:
Open Square bracket = alt + (
Close Square bracket = alt + )
You can also use the Keyboard Viewer to find out where the keys are.

The software doesn't allow the use of these characters 😟

I'm using azerty non-english P

In the Belgian layout it should be Option/Alt + Shift + ( and ).

You are right. I tested with the french keyboard (I will retire in shame 🙂 ).