thanks for you help! Since asking this, I have learned more precisely what I'm looking for. The techniques I would like to implement are described well here: http://reliawiki.org/index.php/Mixture_Design
MatLab's Design of Experiments functions are available here https://www.mathworks.com/help/stats/design-of-experiments-1.html , but I don't see any options for design of experiments of mixtures using simplex centroid, simplex lattice, or extreme vertices methods, and I'm unsure whether existing functions could be modified to accommodate this.