General Syndulla was called over the loudspeaker at the Rebel hangar on Yavin just before the Battle of Scarif (along with a cameo by Chopper and The Ghost) in Rogue One. Hera was then shown to be present after the Battle of Endor in episode 14 of The Forces of Destiny cartoon shorts.
Now, a new Forces of Destiny comic series has placed Hera at the scene of another pivotal location from the OT. The series was announced at NYCC in October, and the first issue, Leia #1, includes Hera. While the extent of Hera's involvement through the issue is unknown at this point, the comic does show her at Echo Base with Leia and Han just prior to the Battle of Hoth. It also isn't clear (yet) if she was a participant in the actual battle, but that information will likely be forthcoming.
Hera is shown in the preview image below, along with a few other comic panels and variant covers, on the German site Jedi-Bibliothek, which translates to "Tenacious Jedi"*
Still no word on any of the other Spectres' post-Rebels exploits, or even which ones survived the show's timeline.