Validate TOTP code towards MFA method

According to the API specifications there: /sys/mfa/validate - HTTP API | Vault by HashiCorp, it is possible to validate a request by using mfa_request_id, the TOTP and the mfa_method_id.

Is there a possibility to validate just a TOTP over a mfa_method_id, without a mfa_request_id?

No, because there would be no context identifying which user the OTP should be validated for.