Send command via qgroundcontrol

hi Im new to qgroundcontrol & mavlink .I want to send mavlink command from qgcs to px4 ardupilot when searching in topics i understand that qgc has custom command widget but i cant find that…
please help me…
thanks…

That is no longer available

thanks for your answer… i can change (flight mode ,arm,…)with put a button
but how can send a custom command ?