I don't have a Steam Deck board handy (It's on my list of would like to haves) and I can't tell in any of the images where that trace might lead. Is there any remnants of the pad, or the trace that you could get a multimeter on? I see a bit of copper, but I can see that most of the plane surrounding that whole area is ground. So my guess is that it goes through the board somewhere.
If you can get any little hint of a nub from that pad, or the trace it should be attached to put your multimeter in continuity mode and poke around until you get a beep. I might specifically check any of the other points in that area since there aren't many components on either side of the board. I'll check some of my usual haunts to see if I can get more info.
UPDATE: 06.23.2024
Got a Steam Deck board to tinker with, coincidentally. Pulled the switch off to see if I could suss this out. Switch came off without incident, but it's very clear that there are no traces leading from this pad, so it definitely goes into the board and comes up somewhere else.
Did some quick continuity testing to see if I could figure out where. No joy on that same side of the board.
Soldered a wire to that pad so I could check for continuity with components on the other side of the board. Wire coating melted back when I soldered it down (and it was slightly too thick a wire, but it's what was handy). Went to bend it a bit so it didn't touch the ground plane around the edge and ripped up the pad. -_-
Pics for humorous failure. I'll get there, but now I have less to work from. See tiny nub of a connection under where the pad was :D
UPDATE 2: 07.01.2024
Sourced from the discord server in the comments below. I confirmed this on my own "for science" Steam Deck board. I have not found anywhere else that this line comes up on my F7A board.
This shot was taken after I removed the ITE IT5570VG. red pad is the one for the power button. Note the microSD card reader's position in the below images for orientation.
So you can definitely repair this, but it won't be easy either way you go. You can do like me and dig the trace out from where it got pulled. But you'll need to be very gentle. The trace is very thin and easily damaged. Travels along the orange arrow
Or you can make an enormously long jumper to the other end of the board. But you'll need to remove the ITE chip since the correlated pad is on an interior row.