What symbol to use for a electronic circuit breaker in a schematic?
depends on the target for the schematic, I mean where I learned protection circuits we draw a box.

You can follow ANSI standard https://www.noao.edu/ets/Mechanical/Policies/ANSI%20Y32.2-1975.pdf

here are some examples of schematics too

https://www.nrc.gov/docs/ML1025/ML102530301.pdf

thing is depending on the country/target audience they might use a different symbol so I think you need to do research about how it works where you live.