@an-andrew If I understand this your fence is two boards that might move independently - like the two ends of a jointer - but on their side. If so...
I would probably define the fence as an axis with both motors. Then, RRF Gcode supports G1 H2 which moves an individual motor and you could fairly easily change the dashboard source or add a custom button screen (see https://plugins.duet3d.com/plugins/BtnCmd.html) that does conventional G1 moves along with G1 H2 for that second half of the fence.