Hollow Knight: Silksong has not been officially released, so the taunt control is not confirmed
Check the in-game control settings or button prompts once the game is available
If you are asking about a demo or preview build, the taunt input may differ by version and platform
Look for an emote, gesture, or special action mapped to a direction, shoulder button, or menu option
If you want, I can help you find the taunt control for your specific platform or build