따로 빼서 unit으로 할까 하다가 귀찮아서 그냥 추가하였습니다.
(물론 그냥 추가하면 dcu때문에 빌드가 안됩니다. 그래서 복사해서 필요한 프로젝트에 사용하였습니다)
환경은 Delphi 10 Seattle입니다.

-----------------------------------------
unit Macapi.IOKit

...

const
  kIOMasterPortDefault: mach_port_t = 0;
  kIOPlatformUUIDKey = 'IOPlatformUUID';

  // add
  kIOPMAssertionLevelOff = 0;
  kIOPMAssertionLevelOn  = 255;
  kIOPMAssertionTypeNoDisplaySleep = 'NoDisplaySleepAssertion';

...
type
...
function ...
...
function IOObjectRelease(anObject: io_object_t): kern_return_t; cdecl; external libIOKit name _PU + 'IOObjectRelease';

// add // AssertionID는 Uint32의 포인터형
function IOPMAssertionCreateWithName(AssertionType : CFStringRef; AssertLevel : uint32_t;
  AssertionName : CFStringRef; AssertionID : Pointer) : uint32_t; cdecl; external libIOKit name _PU + 'IOPMAssertionCreateWithName';
function IOPMAssertionRelease(AssertionID : uint32_t) : uint32_t; cdecl; external libIOKit name _PU + 'IOPMAssertionRelease';

---------------------------
example.


TForm1 = class(TForm)
  procedure BtnDisableClick(Sender: TObject);
  procedure BtnEnableClick(Sender: TObject);
private
  FSleepAssert : UInt32;
public
end;

implementation

uses
  Macapi.IOKit, Macapi.CoreFoundation;

............
procedure TForm1.BtnDisableClick(Sender: TObject);
begin
  FSleepAssert := 0;
  IOPMAssertionCreateWithName(CFSTR(kIOPMAssertionTypeNoDisplaySleep), kIOPMAssertionLevelOn, CFSTR('MyProject is Good'), @FSleepAssert);
  if FSleepAssert = 0 then
    ShowMessage('Disable Failed!!');
end;

procedure TForm1.BtnEnableClick(Sender: TObject);
begin
  if FSleepAssert > 0 then
    IOPMAssertionRelease(FSleepAssert);
end;