VO-SWMM provides following snapping tools.

Icon Command Icon Command Icon Command Icon Command
Point
Allows to snap to a point.
EndPoint
Allows to snap to the end point of polyline or polygon. (Available only in ArcGIS)
Vertex
Allows to snap to the vertex.
MidPoint
Allows to snap to the middle point of a polyline
Edge
Allows to snap along the edge of polyline or polygon.
Intersection
Allows to snap to intersection of two geometries