You have to create both portals first, to create the marker, and then pass it to the launch portal.
Marker = Reach portal
Put marker in Launch portal.
Can be different beacon owners, but you need to be able to interact inside the beacon. Pixel gate portal it was Karokendo's beacon, Therka it was Pharaonah, and Dragons watch it was mine.
But to link, you need to be able to interact, so you can fuel it and put the marker in.