Just make a small line using split poly tool where you want to detach the object, than delete thoughs small faces.
The object will still be one even though it will apperes to be 2. Than go edit polygon> seperate.
Now you will have 2 objects...
I am enough of an artist to draw freely upon my imagination, knowledge is limited, imagination encircles the world. (Albert Einstein)
https://www.artstation.com/kurtb