To disconnect from a remote shared USB device from the client side, select it in the list and click Disconnect:

The device will become inaccessible for the usage on the client side. It will not be removed from the list, so you can reestablish connection with it at any moment.

Warning: a disconnected USB device still remains shared on the server side, therefore it is inaccessible for the local usage (on the server). Refer to this section to find out how to unshare USB device on the server side.