Moving Objects Symmetrically with a Fulcrum-selected Mirror Plane
Examples

Pivoting an edge modifies the matching geometry on the other side of the fulcrum-selected mirror plane.

Moving faces that are symmetric to each other but lie partially on either side of the mirror plane. The center of each of the objects' bounding boxes is on either side of the plane, so the symmetric move tool can detect the symmetric geometry and the angled faces can be moved