I cannot place the portal with the Gateaway Key. Instead of placing the portal it just cycles through the possibilities making it
impossible to place a portal. (Mk1)

• Minecraft: 1.12.2
• Forge: 2854
• AbyssalCraft: AbyssalCraft-1.12.2-2.0.0-ALPHA-2

Portals are no longer placed by the key as of 2.0.0, instead you create portals through a ritual. Right-clicking the key merely cycles through the available dimensions you can create portals leading to, but the ritual is where the actual portal is created.

Is the ritual already implemented?

Yeah, it was implemented in the same release as the keys had their functionality changed.

Can I look up the ritual somewhere or is it only implemented in the code?

Like all rituals, it's viewable in the Necronomicon in-game. I don't know if anyone has posted a screenshot of the page with the ritual.