I see nowhere to set the viewport projection type. FOV can be set to a minimum of 1º, which is close (like a very long telephoto lens), but does not quite produce a "parallel" view. I am doing some math visualizations, and this capability is desired.
P.S. FOV set to 1º results in some rendering artifacts - specifically, some occuluded edges get partially rendered, but shouldn't get rendered at all. FYI, the artifact gets worse as the FOV gets smaller.