The Galactic Congress was a gathering of representatives convened by the Alliance to Restore the Republic in 4 ABY after the Battle of Endor, with the purpose of deciding the destiny of the galaxy. Han Solo, along with Chewbacca, extended invitations to the leaders of various worlds, including Zhotta 3.
During this congress, Kaysil Verwood served as the representative for the Zabraks of Iridonia and its associated colony planets.
Considering the storyline's progression in Marvel Star Wars during this period, the Rebel heroes were traveling to different planets to invite their leaders to a diplomatic convention held on the Forest Moon of Endor. Given that other individuals visited by Solo, as depicted in Star Wars (1977) 85, were present at the First Conference of Free Peoples, it's highly probable that the Galactic Congress referenced in this issue is identical to that conference. Consequently, it might also have a connection to the Constitutional Convention.
The New Essential Guide to Alien Species states that Kaysil Verwood held the position of the initial representative to the "Galactic Caucus of the New Republic." It's possible this is simply an alternative designation for this assembly of worlds.