Windows 10 equivalent of LaunchAdvancedAssociationUI

To open the Set your default programs page:

%windir%\system32\control.exe /name Microsoft.DefaultPrograms /page pageDefaultProgram

Reference: https://msdn.microsoft.com/en-us/library/windows/desktop/ee330741.aspx

Note: This method does not work with April 2018 Update.

To open the Choose default apps by file type page:

Activator->ActivateApplication(    L"windows.immersivecontrolpanel_cw5n1h2txyewy"    L"!microsoft.windows.immersivecontrolpanel",    L"page=SettingsPageAppsDefaults"    L"&target=SettingsPageAppsDefaultsFileExtensionView", AO_NONE, &pid);

Version 1709 or later

To open the Set defaults by app page:

Activator->ActivateApplication(    L"windows.immersivecontrolpanel_cw5n1h2txyewy"    L"!microsoft.windows.immersivecontrolpanel",    L"page=SettingsPageAppsDefaults"    L"&target=SettingsPageAppsDefaultsDefaultAppsListView", AO_NONE, &pid);

Changing the system default apps is no longer allowed. Here is the annoucement on the Windows Insider blog:

Changes to how Windows 10 handles default apps: ‘Default apps’ refers to the way that Windows maps file types and protocols (like HTTP) to the Windows applications they open by default. For example, your favorite photo editor may be set as the default app for .JPG files, which means that when you double-click on a .JPG file in File Explorer, it opens in that photo editor. In Windows 8.1, Classic Windows applications (Win32) could invoke the prompt asking you to change your defaults, so you may have seen multiple prompts during install and after they launched. However, Windows Store apps could not invoke this prompt. Instead, a notification banner will appear after your apps are installed telling you that new apps are available and you would click on this banner to change your defaults.

We know your defaults matter to you. With Windows 10, all apps – both Classic Windows apps and Universal Windows apps – will be unable to invoke a prompt to change your defaults, only Windows. You remain in full control of your default experiences, while reducing some of the unwanted noise that multiple prompts can bring.

Even if there is some way to launch the settings application, you will not be able to do more.

• Open the main Default Programs window in Control Panel:

  %windir%\system32\control.exe /name Microsoft.DefaultPrograms

• Open the Set your default programs page:

  %windir%\system32\control.exe /name Microsoft.DefaultPrograms /page pageDefaultProgram

• Open the Set associations for a program page:

  %windir%\system32\control.exe /name Microsoft.DefaultPrograms /page pageDefaultProgram\pageAdvancedSettings?pszAppName=YourAppRegName

  YourAppRegName is name of your registered application from HKEY_LOCAL_MACHINE (or HKEY_CURRENT_USER)\SOFTWARE\RegisteredApplications that must be escaped (Use UrlEscape, Luke!) before use. For example:

  %windir%\system32\control.exe /name Microsoft.DefaultPrograms /page pageDefaultProgram\pageAdvancedSettings?pszAppName=Internet%20Explorer

• Open Associate a file type or protocol with a program page:

  %windir%\system32\control.exe /name Microsoft.DefaultPrograms /page pageFileAssoc

• Open Change AutoPlay Settings page:

  %windir%\system32\control.exe /name Microsoft.AutoPlay

• Open Set Program Access and Computer Defaults page:

  %windir%\system32\ComputerDefaults.exe

P.S. Also you can use IOpenControlPanel::Open method to open Control Panel item/page instead:

IOpenControlPanel * OpenControlPanel;HRESULT Result =  CoCreateInstance(CLSID_OpenControlPanel,    NULL, CLSCTX_INPROC, __uuidof(IOpenControlPanel), (void**)&OpenControlPanel);if (SUCCEEDED(Result)){  const wchar_t * Page = L"pageDefaultProgram\\pageAdvancedSettings?pszAppName=YourAppRegName";  OpenControlPanel->Open(L"Microsoft.DefaultPrograms", Page, NULL);  OpenControlPanel->Release();}