Extract can also be used in edit mode.
Hotkey >> Y (during draw)
Extract is intended to take the underlying surface and convert it into a cutter.
As of 71V extract is also capable of taking surfaces.
Edit Mode Extract
Extraction can be used in edit mode which will switch to custom cutter with the resulting extraction.
Using active Only as a jumpoff point
Active only seems useless however not being able to cut the secondary selection and instead use it for obtaining orientation is a powerful feature.
I used object scroll from hardOps to get the cutter for the main cylinder that I used to orient my extraction to. I tend to start in red just to see what I'm going to take disappear and then press Y to toggle before application to extract.