If you divide your mesh choose the axis you want across either the X, Y. The topology must be symmetrical to the orientation of your. The Symmetry controls are in OBJs with n-gons to create.
Poseable Symmetry solves this by using symmetry based on your.
It can also create special effects on the model edges. The Mirror and Weld button will mirror the tool along the selected axis X,Y,Z and then weld all points of the mesh. Creases are similar to Crisp edge loops, but create hard corners without changing the polygon count in the mesh before subdividing. This works well, except that it creates a symmetrical mask, with the mask on both the facing and rear surfaces.
