using alternate prompting inside when to from

[sadsilly]

so I was wondering if it possible to change.
[A|B] <-- this
or
[C:D:step] <-- this to {}

example being {C:D:step}

reason I ask is because if you write
[C[A|B]:D:step]

it breaks [A|B] an stop working as a syntax an will only read A. I am assuming it because it crashes in to first ] before second.

if it not possible I understand I do not know much of how coding works I just find prompting with these syntax very fun I would like more depth., <3