Running a Windows Debug build built with 6.9.0 and then closing the application I get:

The thread 25544 has exited with code 0 (0x0).
No memory leaks detected.
Visual Leak Detector is now exiting.
The program '[63732] DeepSkyStacker.exe' has exited with code 0 (0x0).

The thread 56164 has exited with code 0 (0x0).
WARNING: Visual Leak Detector detected memory leaks!
---------- Block 623 at 0x000000000293B000: 48 bytes ----------
  Leak Hash: 0x03B19E03, Count: 1, Total 48 bytes
  Call Stack (TID 68304):
    ntdll.dll!RtlAllocateHeap()
    clbcatq.dll!0x00007FFE66085F8F()
    combase.dll!0x00007FFE674049A1()
    combase.dll!CoGetModuleType() + 0x6E5A bytes
    combase.dll!CLSIDFromProgID() + 0xA4B bytes
    combase.dll!RoGetActivationFactory() + 0x352 bytes
    combase.dll!RoGetActivationFactory() + 0x5F bytes
    qwindowsd.dll!0x00007FFD2BF81530()
    qwindowsd.dll!0x00007FFD2BF81330()
    qwindowsd.dll!0x00007FFD2BF81082()
    qwindowsd.dll!0x00007FFD2BF7FF66()
    qwindowsd.dll!0x00007FFD2BF805E4()
    qwindowsd.dll!0x00007FFD2BF85AFA()
    qwindowsd.dll!0x00007FFD2C0107EE()
    qwindowsd.dll!0x00007FFD2C00F6BB()
    qwindowsd.dll!0x00007FFD2C00FBEA()
    qwindowsd.dll!0x00007FFD2C00F604()
    qwindowsd.dll!0x00007FFD2C00DBD9()
    qwindowsd.dll!0x00007FFD2BF7A185()
    C:\Users\qt\work\qt\qtbase\src\gui\kernel\qguiapplication.cpp (1379): Qt6Guid.dll!init_platform() + 0x2F bytes
    C:\Users\qt\work\qt\qtbase\src\gui\kernel\qguiapplication.cpp (1591): Qt6Guid.dll!QGuiApplicationPrivate::createPlatformIntegration() + 0x9A bytes
    C:\Users\qt\work\qt\qtbase\src\gui\kernel\qguiapplication.cpp (1613): Qt6Guid.dll!QGuiApplicationPrivate::createEventDispatcher()
    C:\Users\qt\work\qt\qtbase\src\widgets\kernel\qapplication.cpp (154): Qt6Widgetsd.dll!QApplicationPrivate::createEventDispatcher()
    C:\Users\qt\work\qt\qtbase\src\corelib\kernel\qcoreapplication.cpp (867): Qt6Cored.dll!QCoreApplicationPrivate::init()
    C:\Users\qt\work\qt\qtbase\src\gui\kernel\qguiapplication.cpp (1640): Qt6Guid.dll!QGuiApplicationPrivate::init()
    C:\Users\qt\work\qt\qtbase\src\widgets\kernel\qapplication.cpp (478): Qt6Widgetsd.dll!QApplicationPrivate::init()
    C:\Users\qt\work\qt\qtbase\src\widgets\kernel\qapplication.cpp (465): Qt6Widgetsd.dll!QApplication::QApplication()
    D:\Github\DSS\DeepSkyStacker\DeepSkyStacker.cpp (843): DeepSkyStacker.exe!main() + 0x1E bytes
    C:\Users\qt\work\qt\qtbase\src\entrypoint\qtentrypoint_win.cpp (45): DeepSkyStacker.exe!qtEntryPoint() + 0xE bytes
    C:\Users\qt\work\qt\qtbase\src\entrypoint\qtentrypoint_win.cpp (64): DeepSkyStacker.exe!WinMain()
    D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl (107): DeepSkyStacker.exe!invoke_main()
    D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl (288): DeepSkyStacker.exe!__scrt_common_main_seh() + 0x5 bytes
    D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl (331): DeepSkyStacker.exe!__scrt_common_main()
    D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_winmain.cpp (17): DeepSkyStacker.exe!WinMainCRTStartup()
    KERNEL32.DLL!BaseThreadInitThunk() + 0x17 bytes
    ntdll.dll!RtlUserThreadStart() + 0x2C bytes
  Data:
    88 66 0E 66    FE 7F 00 00    01 00 00 00    DD DD DD DD     .f.f.... ........
    00 00 00 00    00 00 00 00    80 A5 93 02    00 00 00 00     ........ ........
    00 00 00 00    00 00 00 00    01 00 00 00    DD DD DD DD     ........ ........

   : 
   : lots of lines omitted
   :

Visual Leak Detector detected 626 memory leaks (74964 bytes).
Largest number used: 2496521 bytes.
Total allocations: 38816395 bytes.
Visual Leak Detector is now exiting.
The program '[2664] DeepSkyStacker.exe' has exited with code 0 (0x0).