After looking around the Mech Land Assault DLCs settlement eDEN Station: The Goose, I found a second button which has been speculated to exist. So what does it do and where to find it? Let's start with what it does once you press both of them. Well,I don't know. And that's because of the second part of the question, where it is. As it turns out, it's beneath the ground. But take a look for yourself:
As you can see, it's about 4 meters beneath the ground near the sphere tank. So how did I find it then? I used a camera hacking tool called Extreme Injector to detach the camera from Rico and take it everywhere I want to. I got quite lucky to find it, because it's really hard to make out from a distance. But this tool only allows me to move the camera, not Rico and in order to press it I need Rico down there. But as it turns out, it's no so complicated to get Rico below the ground. Jets, which are carried by the trains on Insula Striate, are, due to a glitch, immune to collision damage. So I fast traveled to Insula Striate, caused a few train crashes until I got one with a jet. As soon as it crashed and came to a stand, I flew off, which causes the train beneath the jet to despawn. The jet falls down and lands safely. It is not possible to pull it down using the grappler, this will cause the collision bug to not work. Also, don't use the grappling hook to enter the jet, either, same thing will happen.
Now that I got my jet I entered it, flew back to eDEN Station: The Goose and took a nose dive into the ground. The jet passed right through and I jumped out before it hit the water (which is everywhere at sea level below the map). I flew back up close to the button using the Bavarium wingsuit and tried to grapple myself onto it. As I tried out before all of this, you can press buttons if you are standing on top of them, so that is what I tried, since there is no ground to stand on beneath the button. As it turns out, it's extremely hard to grapple onto the button and not fall down again or accidentally grapple through the ground and end up back on the surface. After about 2 or 3 hours I managed to land on top of it. But the game decided to push me through the ground and I ended up back on the surface. But while I was standing there for about 1 second, no option to press the button appeared. Actually, there was no animation on the button either. Pushable buttons have an animated white stripe on them, this one didn't. So maybe it's not possible to push this button at all.
I'd like to ask all of you who are interested in this, to go and try this out for yourself and see if you can press this button. Any thoughts or ideas?
What if you're suppose to push the first button first? The first button does make a sound, but we don't know what, if anything, it does. Maybe it enables the second button? And the second button is reset once the game loads?
To avoid the possibility of a reset by game loading, you should not use Fast Travel, or even look at the Map after pushing the first button.
I happen to know that some things are reset even if you only look at the map. Example: I was using the barge to transport the large anchor from the Weapons Shipment Yard. The anchor was not connected to the barge, so when I looked at the map, it disappeared. Connecting the anchor to the barge vie the Grappler would prevent it from despawning.
You are right, I just used the camera hack to look at the button after I pressed it and became pressable. The problem with this is, in order to get below the ground I need to leave the area to get the jet. Even if I park it neraby beforehand, I have to pick up speed in order to get trough the ground.
We thought nothing would happen after pressing the first button too. Now we either have to find the third button, or look really hard to see what it could have changed. Maybe it unlocks the Mech for a player who doesn't have it yet? How would we even know?
The second one does work, if you read the above. The first one has to be pushed first. That will make the second one pushable. But the right now we just don't know what if anything the second one does. Just like we didn't used to know what if anything the first one did.
Original poster here, I haven't looked into it since I made this post. If anyone likes to take a look around for themselfs, just install the ghost mode mod and feel free to check beneath the surface for any other buttons.