I’ve check FastDraft and that option is available on NEC4 contracts, and relates to clause 16. Contractors Proposals.This allows the contractor to propose to the Project Manager that the scope is changed, and if accepted the Contractor can quote. The Contractor may also propose an area to be added to the Working Areas.
The Contractor or Project Manager can also propose acceleration to achieve Completion before the Completion Date. A similar query regarding proposals has been raised below.
If you were to create a Draft communicaiton, FastDraft will tell you the applicable clause so you can investigate further, but i would check your contract.