Unshare All - click it to restrict access to your local USB dongles and disconnect all active clients.
Disconnect All - click it to disconnect all client computers from your local devices and all remote devices from your local computer. USB dongles shared on your local machine will remain available for remote connection.
Remove All - click it to unshare all USB dongles and remove them from the device list.
Also, there are additional options that allow you to control connections to USB dongl shared on your computer:
Disconnect - select it to disconnect a remote computer from the device shared on your Mac.
Resend Invite - if a remote user declines the invite they receive from you, you can use this option to send the invite again.
Remove from List - click it to unshare the selected device and remove it from the device list.