When going to the End dimension, then using the /setblock command to place a Nether portal block (Nether portals don’t work in the End), teleports you back to the Overworld, exactly where you were before going to the End, but at Y=32767. However, going to the End from the Nether via the /setblock command (End portals don’t generate in the Nether) takes you to the normal End dimension