Version 1.5.0 of the declarative pipeline plugin added support for matrixes. However, these are not rendered very well by Blue Ocean. It just says "Matrix ..." next to each set of parallel stages. You have to hover over this cut off label in order to see what the values of the axes are. This should be cleaned up so the values of the axes are always visible. One possibility is to add a pseudo-stage at the start of each parallel block whose name is the list of values.