Starborn Armor scaling can be enabled in game by using the DarkStar Terminal located in one of two locations. The first is in The Lodge, down in the basement, on the wall next to the Mark 1 spacesuit case. The other is attached to the side of the machinery on your DarkStar Terminus at your outpost.

Once enabled, you are given a hidden Perk. This perk persists through NG+, and "flips a switch" in the Leveled List that rewards you for passing through the Unity. Your number of trips is counted, and then used to select your reward.

As you are aware, the Starborn armor you normally receive changes graphics as you pass through each successive Unity, up until your 10th trip. The first is Astra, and second is Materia, etc. This finally ends with Venator, which is the last suit you will ever receive no matter how many Unity trips you make in the base game.

When Starborn Armor Scaling is enabled, this graphical change becomes a rotation. Trips 1, 11, 21, 31, 41 all grant you Astra, but with scaled up stats. Trips 2, 12, 22, 32, 42 grant you Materia, but with scaled up stats. This continues for every suit in the list, each repeating every 10 trips until trip 50.

Once you pass through Unity, you can also visit a Starborn Services terminal, provided in the basement of The Lodge or next to the Trade Authority kiosk on the DarkStar Terminus. This terminal sells the tier of suit you have unlocked. IE, if you've completed 23 trips through Unity, you will be able to buy ANY suit graphic with Mark 23 stats. This also lets you buy extra suits and outfit your companions, or rest to reset the vendor and "reroll" your suit's stats & legendary effects with greater ease.