HEAPIDX.H

The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the HEAPIDX.H header at

d:\th\minkernel\ntos\rtl

and draws from it the following type definition:

Line Number Type
57 struct _HEAP_LIST_LOOKUP

The header HEAPIDX.H is not known in any Device Driver Kit (DDK) or Windows Driver Kit (WDK).