I'm using multisite with different users. I need a way for users to get back to their home page

I'm using multisite with different users/stores. I need a way for the store administrators to return back to their main site. Like a short code that I can place in the main menu or in a widget. Right now, when managing their store in a front end store manager, there is no way for them to return to their store without typing it into the URL.