For USB-C it's probably not needed to create your own schematic symbol. KiCad already has several symbols for USB-C connectors (depending on which pins you want to use). Pin numbers and naming on USB-C connectors is also standardized (A1 though A12 and B1 though B12) and this makes it a lot easier to make a "universal" symbol for it.
https://en.wikipedia.org/wiki/USB-CKiCad uses "pin stacking" in a lot of it's default symbol libraries, as Ataradov already mentioned. You can easily se how that works by loading a schematic symbol in the symbol editor.
And another part of the puzzle was mentioned by Selcuk. If pads on in the footprint have the same padnumber, then KiCad interprets this as all those pads have to be connected together (when connected to a net).
And third.
USB-C is a bit of a complicated standard, and not all pins are always needed. If you want to use the connector for older USB standards, then only GND, Power, and D+ / D- may be enough.
For the footprint. As always with connectors, you have to be very careful here. The "mating part" of connectors is standardized but the footprint on the PCB is not. There can be hundreds of different footprints for the "same" connector. A quick count shows there are already 24 different "USB_C Receptacle" footprints in KiCad's default libraries.