Hello @AllPaintedGold ,
The ZModeler> Edge> Add Edge To Curve feature does not support Symmetry at the current time. You would need to either manually add the active curves to the exact same edges on the other side of the model as well, or mirror the changes to the other side (Geometry> Modify Topology> Mirror and Weld) after the operation. The latter will avoid any of the targeting issues that may cause symmetry to fail when working at extremely low polycounts.
Additionally, the Zmodeler Bevel feature is not designed to work with 2D geometry. In order to get the expected results on the edges you would need to extrude the plane into a closed 3d volume.
thanks for your reply syndel. so my goal was to get round corners. what is the best approach to get this done ?