RE: Workflor responsable to set bookable bookableresourcebooking to cancelled when work order is set to Close posted
This is not handled in a workflow; it is handled in a plugin which cannot be disabled without many other unintended repercussions. Field Service does not support disabling SDK steps.
If the work order has been posted, Field Service has no reason for incomplete bookings to stay in a non-canceled, incomplete status. If the bookings are "scheduled" for example, it is simply confusing to keep the booking as scheduled even when the work order has been posted. It would imply there is further work required for that booking even though the work order is already posted to the books.
If there is a use-case that you think needs consideration in this area, please consider opening an idea on the topic: Categories (dynamics.com)