The Layer preferences allow you to dictate the behaviour of layers and groups.
Enable Click-Through for New Groups
When selected, any new groups created will have their containing layers instantly accessible without the need to hold the Command key to select them. With any group selected, you can individually toggle this option per-group via the Inspector.
You can learn more about the click-through option here.
Offset Duplicated Layers
By default, Sketch offsets duplicated objects by 10 px from the original. If you deselect this checkbox it will be pasted straight on top of the original.
Rename Duplicated Layers
If selected, Sketch will append “copy” to the layer’s name to ensure the layer name is unique. If unselected, layers will share the same name as the original.
This option allows you to select what resolution you would like bitmaps images to be flattened to, with the Layer › Flatten Selection to Bitmap command. If you are using a Retina display, flattening to a 2x resolution is suggested.