Simply don't. Powering the RPi via the gpio is possible but bypasses all protections (over/reverse voltage, shortcircuit). Do it only if you know for sure that those things won't happen. Otherwise, know that you might kill your pi.

If you still wanna do it, look for ground (gnd) and a +5v rail on the ender 3 board. The here is the rpi gpio pinout, you have to connect gnd to gnd of the board and +5v to the +5v rail on the board.

I guess a good compromise would be to connect the +5v coming from the ender 3 to the proper pads/vias under the microusb cable on the pi, that way you would still have all the protections in place on the pi. But I have never done that, so don't quote me on that.

I just used a buck converter and a USB pigtail for mine so it still plugs into the pi where the power cable used to it's just running off the Ender 3s power supply. They were fairly cheap on Amazon something like $6 for a pack

The only cables you really see for my printer are the short USB connecting the Pi to the SKR on the back, and the power supply cable. The rest is hidden or inside cable chains.

Definitely made moving the printer easier and much less of an eyesore of wiring.

One thing that I'll add in is that I started with a similar setup, but I've heard it isn't ideal to be turning your pi on and off all the time without a proper shutdown sequence. I have my printer psu and filament dryer both plugged into smart plugs. Klipper is connected to home assistant wirelessly so I can turn them both off when prints finish, at idle, etc. My printer is in an enclosure, and the psu, pi, and mainboard both sit outside to keep them from getting hot. Pi has its own charger. I don't find it to be a burden to have the pi and psu both plugged into outlets rather than only having one plug. I find it to be a lot more stable for troubleshooting and any power issues that have come up.

Just so you know, I also started off with the teaching tech all in one electronics box. I spent a ton of hours modifying it for my particular sbc and printer. I guess I ran into issues when I would have to take out one of the boards to work on it, lol. The tolerances were really tight and it was just a pain to get it out from behind. I still have the pi+mainboard both in a box, but it's a new one I designed later on that just sits on a shelf below the printer (wires come through a hole). I find it to be really useful for printing ABS and other hot filaments and keeping a clean and tidy enclosure.

If you google "skr mini e3 v2 pinout" you can find 5v and ground pins. The question is how much load is already on it's 5v regulator and how much are you adding.

You can power the pi from a buck converter or from whatever else.

They apparently make an addon 5v buck converter for that board.

Using a multimeter could help avoid frying more stuff.

Is your pi using Ethernet? If so, maybe go with a PoE hat+injector and use that to save cables instead?

Here is an alternative Piped link(s): https://piped.video/yW9ovo9CHi0?t=320

Piped is a privacy-respecting open-source alternative frontend to YouTube.

I'm open-source, check me out at GitHub.

Here's some official info on this: https://github.com/raspberrypi/hats/blob/master/designguide.md#back-powering-the-pi-via-the-gpio-header