How to put Firefox in Window 10 - Autostart?

On a notebook with Windows 10 Pro I can't insert the firefox.exe with drag & drop or with ctrl c & v. For this I use an icon on the desktop or the firefox.exe on c:. The "Autostart" task manager window does not appear to be active. How can I solve the problem?

Unfortunately, it is not clear from your description whether you have tried the usual way that would be:

Windows key + R
Enter shell: startup and confirm with OK
Search for the EXE and drag or copy it into the opened autostart folder

Maybe it's also because you're not logged in as an admin.

For an even bigger layman, I set up a notebook for one user only. Maybe I have to set up an admin?

I've now set up the admin, but that doesn't work either.

Didn't understand the difference between the window opened with the shell and the window opened in the task manager. It worked when it was moved to the window opened by the shell.