Is it possible to perform Fixed Null Beamforming using the Phased Array System Toolbox?

So, I recently got interested in the field of microphone arrays, and the Phased Array System Toolbox has helped me a great deal understanding the concepts of this area. However, there are still many tasks I find rather difficult to achieve.

Is it possible to configure any of the wideband beamforming algorithms provided by the toolbox in a way they not only enhance the signal from a given direction, but also attempt to cancel signals from other known directions?

Let's say I have a recording of N competing sources using an M-element microphone array. For the entire recording, the location of all sound sources are known.

By what I have read in the literature, in case the interfering sources' locations are unknown, adaptive beamformers (as the Frost algorithm, 'phased.FrostBeamformer') try to adaptively estimate the M filters that best do such emphasis and de-emphasis of the source of interest and the competing ones, respectively.

How about the case all sources' locations are known?

I am aware the 'phased.FrostBeamformer' object supports training data as an optional parameter of the 'step(...)' function, and the object also has the fields 'DiagonalLoadingFactor' and 'FilterLength'. Some parametrizations are also available for the 'phased.TimeDelayLCMVBeamformer' object.

Is it possible to tune them in such a way the described behavior is achieved?

Simply running them using the defaults parametrization produce audibly poor results. The focused sound source is unnotably enhanced.

Thank you very much in advance!