Where are stored the contents (the menu items) ?

[areavailable]

The menu items and subitems

[ge0rdi]

Right-click on Start button and select Open (or Open All Users).

[areavailable]

Thank you for replying.

[ge0rdi]

Those look like recently/frequently used programs (though hard to say as the menu on the picture is not complete and not sure what your settings are). They are populated automatically based on what you are using the most.

You can change settings for them in Show recent or frequent programs setting.

[areavailable]

Not the recently/frequently used. A static list.
Menu's left column (of two) is in picture.

[ge0rdi]

Oki, you mean pinned items. Those are stored in %APPDATA%\OpenShell\Pinned.

You can right-click on an item there, select Properties and in General tab you will see path to the shortcut file.