Sadly rather topical after the murders in New Zealand and a thread for maximum visibility. The 40 page CREST report refers to six models:
This directory has been assembled from frameworks that have been developed in recent years to assess aspects of extremist violence, a term used here to encompass terrorist violence that is framed by ideology and targeted violence that is framed by idiosyncratic beliefs.Each of these frameworks was developed in a slightly different context, and optimised for a different purpose and group of users.
These all conform, to a greater or lesser extent, to an approach that structures professional judgment from a number of potential indicators of risk derived from clinical and correctional research and practice, with the exception of the IVP framework that consists of a checklist for the assessment of escalating behaviours that open source research suggests correspond with more serious intent and/or imminence of attack.
None of these frameworks claims to be able to straightforwardly predict future violence.

The author's slim bio:
Monica Lloyd joined the University part time on retirement from the National Offender Management Service. She helped to establish the new combined forensic and clinical doctorate training and her specialism is the Psychology of Extremism and Terrorism.

The main CT thread into which this is likely to be merged is: