There have been few changes since the 2018 Heliophysics Fleet. Van Allen Probes and SORCE have been decommissioned, while Solar Orbiter, ICON and SET have been added. As of spring 2020, here's a tour of the NASA Heliophysics fleet from the near-Earth satellites out to the Voyagers beyond the heliopause.
Excepting the Voyager missions, the satellite orbits are color coded for their observing program:
Magenta: TIM (Thermosphere, Ionosphere, Mesosphere) observations
This visualization presents orbits of the current heliophysics satellites covering the space near Earth, out to the Sun-Earth Lagrange point, L1, and finally a view of the current missions operating in the inner solar system.
Solar Orbiting Fleet:
STEREO-A: The remaining STEREO spaceraft orbits the Sun in roughly the same orbit as Earth. SVS page
This visualization presents orbits of the current heliophysics satellites covering the space near Earth, through the solar system, and concluding with a view of the Voyagers, just outside the heliopause.
Voyager 1 & Voyager 2: The two Voyager spaceraft orbit originally performed flybys of the outer planets of the solar system but continued to operate. They are now the most distant monitors of the plasma in the space between the stars. At the time of this visualization, Voyager 2 has just crossed the heliopause.SVS page