I chan't change into a Launcher of type Directory when in
applications:/// to add more Launchers.

Steps to reproduce:

1. go to applications:////
2. create a new launcher of type Directory
3. Try to change into that new Launcher Directory 
to add additonal Launchers and Submenus.

Result:

You get the error:

applications:///foo.desktop
'This is a test Nautilus content view component'

Expected Result:

Nautilus should let the user change into the directory to allow 
creating of Submenu and Sublaunchers

uhh this really notabug. Directory type launchers are not traditional
directories (folders) that you are thinking of. They are files used
with in virtual directories that are used for translation purposes.
I'm going to mark this a dupe of 95331 which recommends fixing the ui
of the new launcher dialog in order to hide all the implementation
nonsense. Please add comments there.

*** This bug has been marked as a duplicate of 95331 ***

I will comment furter on 95331 , but I think you're missing the point
here. I for sure know that this launchers are special vfolders files
marked with "Type=Directory". But the jumping point is how should a
User add, Menus and Submenus, when they can't change into the Menu
they just created.

So I do not suggest that Nautilus should *always* change into Files of
Type=Directory, but it must change into it when in applications:/// to
add further submenu's and other entries. The other behavior, that
Nautilus normally displays just the icon, which is stated in the
.desktop file is correct.

3. Otherwise describe an intutive way for a user how he/she could get
the following result:

Adding a new Menu "Foo" into the Root Menu, then adding more Submenus
in Menu "Foo".

When you do it the proposed way via applications and not using vi or
whatever editor to create the files on your own, this is not possible.