RtlQueryProcessPlaceholderCompatibilityMode - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _NTRTL_H
#if (PHNT_VERSION >= PHNT_REDSTONE4)

NTSYSAPI
CHAR
NTAPI
RtlQueryProcessPlaceholderCompatibilityMode(
    VOID
    );

#endif
#endif

View code on GitHub

This function is documented in Windows Driver Kit.