Super Administrators role, can't share everything?

my problem, a user (called Admin2) with admin role and additional with membership of a toplevel2 folder group, can not share e.g. [subfolder A2] to a user. Why?
User Admin2 is member of toplevel2 folder, but can not share any sub-folder.

[toplevel2 folder]
----- > [main-folder A]
---------- > [subfolder A1]
---------- > [subfolder A2]
---------------- > [subfolder A2.1]
---------------------- > [subfolder A2.2]
----- > [main-folder B]

Only if the Admin2 user is added to share recipients of the specific [subfolder A2], than Admin2 can share [subfolder A2] to other users.

How can Admin2 share everything?

Latest admin manual says “simply add them to the admin group.”

Granting administrator privileges to a user

Thank you very much.