Question for setting permissions for Shared Mailboxes with exchange online

I'm trying to create a access template for administrating shared mailboxes in exchange online.  The only things that I want are:
read all properties
add/remove send as
add/remove Read and manage (full control)

I was able to do the send as with exchange online distribution groups but I don't see the same properties for shared mailboxes.  Looking for the object properties.  I'm guessing I'm just missing something but maybe the functionality isn't available.  I don't like the built in templates because I basically want our help desk to just be able to add/remove members but not be able to editing the mailbox properties.