Exactly, sure you could have relays or Automatic Transfer Switches like we use from generators. But if you're just slamming more power at stuff than it's meant to use, where's your overcurrent protection?
one of my favorite jokes about this is on TNG. i think it's the episode where the bridge gets cut off from the rest of the ship, and Troi is in charge of running the ship. O'Brian makes a comment to Ro about how you can't 'just reroute power from things'.
I don't know about you people, but personally, I always write programs at work by removing boards from my computer and plugging them in a different order.
Well, it really wasn't. You'd program by punching the cards, and then insert them into the computer. If they brought the boards from a terminal (or replicator), and switched the old ones to the new ones, the entire thing would make sense.
It's a bit similar to how people programed analogical computers at the 50s. But it's actually a lot like programing old sewing machines. The thing those have in common is that their programs were always an order of magnitude smaller than this comment.
Judging from what things look like when they open up the walls, they could just be telling the system to use a specific circuit path. It looks like everything is just a bunch of blocks or cards with super dense computer chips on them and half the repairs we ever see are just these being unslotted and replaced. The other half being waving fake tools around.
you can't just "re-route power" by pressing buttons on a screen and not, you know, actually unhooking any wires!
High-voltage switches might be a bit complicated. One I've seen requires you to tighten a spring and then have it released extremely fast to prevent sparking. Still, there should be a way to do it safely, without having to go near or touch the wiring.