This may be the most obvious use of the USB port, but people seldom use it: Operating the 3D printer using a computer connected via USB.
Software like Printrun (Pronterface) and Simplify3D provide a control interface that allows fine control of your Ender 3 when you connect it to a computer. For instance, you can monitor temperatures, send custom G-code, manipulate motor speed, and move axes fairly easily.
If you’re in a fix and need a fix, try out some control software next time instead of the LCS screen and scroll wheel.
Feature image source: YouTube / Dave Gatton