List Management on Fluent Booking reservations

On Fluent Booking, I would like to add an specific tag or list if on the questions section the user marks a checkbox.

Basically: I want to add them to an specific list (newsletter) if they opt in for that list. If not, they go to the general, not marketing, list.

I looked for this on Fluent Booking but was not possible. Or I did not find it.

I tried looking with FCRM automations: Trigger (New Booking) > Condition --> (Checkbox true) --> But this is not an option on conditions... This is, we can not use on the condition element any booking info.

How can I achieve this?

Use case: Someone enters the calendar, marks the checkbox (A) True: enters into the default list + newsletter; (B) False: Just default.