How can I define my own neighbourhood templates or updating an already existing template?
Currently, each entry of the neighbour-structure needs to have two fields: 'label' and 'neighblabel'. cfg.neighbours must be a struct-array, with each entry having these two fields. You can then define the structure as follows:
cfg.neighbours = struct; cfg.neighbours(1).label = 'Fp1'; cfg.neighbours(1).neighblabel = {'Fpz'; 'AFz'};
Similarly, you can load a template and then change the neighbour definition. Note, that you should verify your definition using ft_neighbourplot.