Configure start menu N770
 

How can I change the entries listed in the menu that shows up, when clicking the last symbol on the left vertical aligned icon (two white windows)?

It's the menu containing Audio-Player, Video-Player links and so on ... I want to put selfmade executable icons, for example to launch a program with customized parameters.

Control panel -> Task navigator -> [Organize]

Unfortunately, I cannot create new icons but only move icons or create folders.

What you likely need to do is to create a custom.desktop file modeled after an existing one and put in the changes that you want. I believe that is how it is manually done in Gnome on the desktop and I would imagine it is the same on the 770. Unfortunately there isn't an easy way to do so via the GUI on the 770 AFAIK.