How to add tray icon behind "start" tray icon, the same as "Search" or "Cortana"

Question

what windows api i can use

Answer 1

Hi，@DJoker
Welcome to Microsoft Q&A！
Is it to add the application icon to the taskbar?

This does not require the use of windows APIs，just right-click on the icon and select “pin to taskbar”.

If you want to create an icon for a new application, refer to the following documentation：

https://learn.microsoft.com/en-us/windows/win32/menurc/using-icons

If you have other questions, you can ask me anytime.
Tong

Answer 2

If you are adding after the start bar just as mentioned above, create a desktop icon and then pin to taskbar.
I wrote a sample based on your needs. It is to create a tray icon on the right side of the taskbar, with two options, and double-click the icon to exit.
Check that if it meets your needs.
#include<windows.h>
#include<cstdio>
#include<stdlib.h>

#include <windows.h>  
#define IDR_PAUSE 12  
#define IDR_START 13  
  
#include <shellapi.h>  
#pragma   comment(lib,   "shell32.lib")  
  
LPCTSTR szAppName = TEXT("project");  
LPCTSTR szWndName = TEXT("project");  
HMENU hmenu;  
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)  
{  
	NOTIFYICONDATA nid;  
	UINT WM_TASKBARCREATED;  
	POINT pt;//recive the cordinate of mouse  
	int xx;//recive the value  
	// do not modified TaskbarCreated  
	WM_TASKBARCREATED = RegisterWindowMessage(TEXT("TaskbarCreated"));  
	switch (message)  
	{  
	case WM_CREATE:  
		nid.cbSize = sizeof(nid);  
		nid.hWnd = hwnd;  
		nid.uID = 0;  
		nid.uFlags = NIF_ICON | NIF_MESSAGE | NIF_TIP;  
		nid.uCallbackMessage = WM_USER;  
		nid.hIcon = LoadIcon(NULL, IDI_APPLICATION);  
		lstrcpy(nid.szTip, szAppName);  
		Shell_NotifyIcon(NIM_ADD, &nid);  
		hmenu = CreatePopupMenu();  
		AppendMenu(hmenu, MF_STRING, IDR_PAUSE, "stop");//two option   
		AppendMenu(hmenu, MF_STRING, IDR_START, "go on");  
		break;  
	case WM_USER:  
		if (lParam == WM_LBUTTONDOWN)  
			MessageBox(hwnd, TEXT("Win32 API doubleclick exit!"), szAppName, MB_OK);  
		if (lParam == WM_LBUTTONDBLCLK)//doubleclick exit.  
			SendMessage(hwnd, WM_CLOSE, wParam, lParam);  
		if (lParam == WM_RBUTTONDOWN)  
		{  
			GetCursorPos(&pt);  
			::SetForegroundWindow(hwnd);  
			EnableMenuItem(hmenu, IDR_PAUSE, MF_GRAYED);//grey section 1  
			xx = TrackPopupMenu(hmenu, TPM_RETURNCMD, pt.x, pt.y, NULL, hwnd, NULL);  
			if (xx == IDR_PAUSE) MessageBox(hwnd, TEXT("section 1"), szAppName, MB_OK);  
			if (xx == IDR_START) MessageBox(hwnd, TEXT("section 2"), szAppName, MB_OK);  
			if (xx == 0) PostMessage(hwnd, WM_LBUTTONDOWN, NULL, NULL);  
			MessageBox(hwnd, TEXT("right click"), szAppName, MB_OK);  
		}  
		break;  
	case WM_DESTROY:  
		Shell_NotifyIcon(NIM_DELETE, &nid);  
		PostQuitMessage(0);  
		break;  
	default:  
		if (message == WM_TASKBARCREATED)  
			SendMessage(hwnd, WM_CREATE, wParam, lParam);  
		break;  
	}  
	return DefWindowProc(hwnd, message, wParam, lParam);  
}  
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,  
	LPSTR szCmdLine, int iCmdShow)  
{  
	HWND hwnd;  
	MSG msg;  
	WNDCLASS wndclass;  
	HWND handle = FindWindow(NULL, szWndName);  
	if (handle != NULL)  
	{  
		MessageBox(NULL, TEXT("Application is already running"), szAppName, MB_ICONERROR);  
		return 0;  
	}  
	wndclass.style = CS_HREDRAW | CS_VREDRAW;  
	wndclass.lpfnWndProc = WndProc;  
	wndclass.cbClsExtra = 0;  
	wndclass.cbWndExtra = 0;  
	wndclass.hInstance = hInstance;  
	wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);  
	wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);  
	wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);  
	wndclass.lpszMenuName = NULL;  
	wndclass.lpszClassName = szAppName;  
	if (!RegisterClass(&wndclass))  
	{  
		MessageBox(NULL, TEXT("This program requires Windows NT!"), szAppName, MB_ICONERROR);  
		return 0;  
	}  
  
	hwnd = CreateWindowEx(WS_EX_TOOLWINDOW,  
		szAppName, szWndName,  
		WS_POPUP,  
		CW_USEDEFAULT,  
		CW_USEDEFAULT,  
		CW_USEDEFAULT,  
		CW_USEDEFAULT,  
		NULL, NULL, hInstance, NULL);  
	ShowWindow(hwnd, iCmdShow);  
	UpdateWindow(hwnd);  
	while (GetMessage(&msg, NULL, 0, 0))  
	{  
		TranslateMessage(&msg);  
		DispatchMessage(&msg);  
	}  
	return msg.wParam;  
}  

Caution, it must be launched as a Windows desktop program.