So far the only selection tools that appear in recap, to my knowledge are:
Fence
Window
Plane
The only issue is these don't always help to quickly differentiate between different features within a scan (cars, trees, buildings, etc.).
It would be useful if there was a way to box select items and hide, save as a scan region or delete. Also if the selection tool snapped to points and essentially created a bounding box that would be really useful.
The only other way i thought it may be possible would be to define points via elevation range or features such as RGB colour to group the points and manipulate as you would desire. The range feature exists in Civil 3D but it would be equally useful in Recap, i believe.