The USB-C port on the back supports DisplayPort Alt Mode, allowing you to display an image from a compatible device and charge it at the same time. It's the only port that supports 90W power delivery, while the USB-C port underneath the left side is only 15W, and the other is an upstream port needed for the KVM switch to work.

If you use the USB-C port for daisy-chaining, you need to make sure you set USB-C Prioritization to 'High Resolution' so that you can get two monitors at 4k @ 60Hz with 8-bit color depth, but once you set it to 10-bit color depth, the signal is unstable. If you set USB-C Prioritization to 'High Data', both displays run at 30Hz.