Focus Modifier: Plan

This modifier projects an area where the effect you have chosen (such as Exchange or Break) will happen. If you choose “full”, it will give you a large area, and if you choose “surface,” it will give you just one layer. Change modes by pressing G (default key). Change size by pressing CTRL+G.

Full:

Surface:

You can combine this with break and it will give you a way to mine huge chunks out at a time (at the cost of Vis):