The Slice Mesh by Plane tool 
on the Cloud/Mesh Tools Tab is similar to the Slice tool
and also in the 3D Viewer. It slices a Mesh along a plane so a suitable Plane
needs to be created first. This tool enables when you have a Plane surface
(either a plane fit through points, or an axes plane, see Planes
and Creating Planes) and a Mesh selected. The
plane will slice through the Mesh and retain the portion of the Mesh facing the
top of the plane. This action is undoable.
The slice will cut through all Meshes that are visible.