• Polyline and points: After you choose an LWPOLYLINE, the routine asks for two points along it, snaps them to the closest points on the curve, and ensures they are not identical before continuing. • Segment extraction: Uses curve parameters at the two picked locations to slice the source polyline between those parameters, reconstructing a new vertex list that represents only the chosen segment (including bulges and widths). • Header cloning: Copies the original polyline’s non vertex DXF data, forces the new polyline onto the chosen target layer, and clears the closed flag so the result is an open segment. • Layer dialog: Builds a temporary DCL file that provides a text filter for layer names, a popup list of matching layers, a button to pick a layer from an existing object, and a toggle to enable or disable Extra transform options. • Layer filtering and pick: Collects all non xref layers, sorts them, filters them dynamically as you type in the filter box, and lets you optionally pick an entity in the drawing to adopt its layer as the target. • Extra options group: When Extra is enabled, the dialog exposes rotation start or end toggle, rotation angle, perpendicular distance, offset style presets, numeric offset, offset copy count, and numeric extension at start and end. • Extension at ends: The extend-ends helper extends the first and last segments of the new polyline by independent distances extS and extE along their segment directions, updating coordinates through COM. • Rotation and distance: Computes a unit direction from the first pick to the second, then rotates the new polyline around the chosen base point (start or end) by the given angle, and moves it perpendicular to that direction by the specified distance. • Offset copies: Creates additional parallel copies of the transformed polyline, spaced by the offset distance along the normal direction, up to the specified offset count; the offset value can be auto filled from presets like DN110, KK I to KK IV. • Persistent settings: Stores the last used layer and filter string in environment variables so that the next run of the command remembers which layer and filter you used previously. • Apply and Undo loop: Wraps operations in a global UNDO group, marks the undo stack before each Apply, and supports stepping back one Apply at a time when you press Undo, without closing the dialog. • Finalization logic: If you never used Apply or Undo, pressing OK performs a single geometry creation using current dialog values; if you cancel, all Apply actions in this session are undone before closing the group.