Windows 11 Drag & Drop to the Taskbar (Fix) is an Open Source app that fixes the now missing drag n' drop to the Taskbar support in Windows 11.
It works with the new Windows 11 taskbar and does not require you to make changes like UndockingDisabled or classic taskbar restoration.
Windows 11 Drag & Drop to the Taskbar (Fix) is designed to detect when you're pressing the left mouse button and determine which taskbar icon you are hovering the mouse pointer over. If the cursor stays in the same area for a defined number of milliseconds, it then simulates the Win+T hotkey and arrow keys to restore the intended window. It also supports dropping files to the Show Desktop button. Windows 11 Drag & Drop to the Taskbar (Fix) supports auto startup and has many configuration options available in detail at the author's site.