Geoff Chappell, Software Analyst
The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the NTSEAPI.H header at
and draws from it the following type definition:
The header NTSEAPI.H is not known in any Device Driver Kit (DDK) or Windows Driver Kit (WDK).
The SE_WS_APPX_SIGNATURE_ORIGIN enumeration has no other reference in the symbol file. It is here thought that the enumeration itself is listed in the symbol file only for being used in an inline routine, possibly also in NTSEAPI.H but certainly not used by any other inline routine in any other header (that contributed to the symbol file).