I have added this request to the tracker:
Issue 2298 – Easier access to Disconnect command
You can vote for it there.

I'm also asking for this...

Ok, thanks for your suggestions.
We will see, if more people ask for this.

So to recap, three things are suggested:

1. Add button "Disconnect session" on "Sessions & Tabs" toolbar
   
2. Add function "Disconnect all sessions"
   
3. Add button "Disconnect all sessions" on "Sessions & Tabs" toolbar
   

Also, a "Disconnect all sessions" option would be fantastic! And a toolbar button to go with it. :D

The tabs even have the "X" button to close them with one click. The toolbar button "Close tab" is the one that is practically unneeded.

"Close tab" is also available on the tab's context menu, but it is available as a toolbar button too. If there's a need for that one-click-less, on the same principle it should be available for the "Disconnect/Reconnect session".

Thanks for pointing out, I wasn't aware of it.
It's still one click more than a toolbar button, which is the same as clicking on the menu and selecting it.

Are you aware that the command is available in the tab's context menu?

Hello, in the menu "Tabs" there is the option "Disconnect session" (or if the session is disconnected, it says "Reconnect session").
Sadly, in the "Sessions and Tabs" toolbar this button doesn't exist. It's useful to disconnect some tabs quickly (without closing the tabs) because it saves bandwidth. I believe this button would not be difficult to implement at all.
Thanks!
Have a good day!