+1 for the first request.
All other functions available from within the left menu panel
When you select an entry in the navigation area on the left site of the screen, the result of your action is shown in the main area on the right side. Selecting »Shared with groups« is the only exception. This definitely confuses users, because they do not expect it. This is a frequent experience when talking to new customers or giving an introduction to a group of scientists about Seafile can be used as an collaboration tool.
I suggest that selecting »Shared with groups« will display my groups in the main (right side) area of the screen as choosing »My Libraries« results in displaying the list of my libraries.
The function for creating a new group should also be found in the same place as the function for creating a new library: On the right side of the grey bar on top of the main area.
PS: Being boringly consistent is a big compliment for an user interface.