Click on Delete Member. The member which has a slab on it can not be deleted.
Click on the joint you want to delete.
Click Ok.
Multiple members can be deleted using select window.
Press left mouse button and drag mouse to select multiple members.
Delete Member (by entering number)
Click on Delete Member. The member which has a slab on it can not be deleted.
Press any key.
Enter desired member number.
Click Ok.