I just made my own symbols for this as well, and then noticed that there are already jumper symbols in KiCad,
Jumper_NO_Small. Whoops! I called mine
It might not be a widespread standard, but solder jumper/bridge symbols aren’t unheard of:
One hiccup: the open solder jumper symbol looks kind of like some versions of the symbol for a neon bulb but without the enclosing circle. I doubt they would get confused in most circuits.
It seems that which symbol is best depends on the situation. To me, the existing symbols slightly imply that a male header and a shorting jumper need to be installed, unless the footprint obviously resembles a solder jumper (not visible from the schematic). Best for end user configuration.
A dedicated solder jumper or solder bridge symbol indicates footprint intent (and lack of an installed component) on the schematic better, but I’m not sure that’s a huge advantage. Best for infrequent hand soldering configuration.
Finally, zero ohm resistors seem best if a pick and place machine is going to be configuring the jumper settings. You just have to manage the BOM and DNI/DNP/DNS flags for the components.