It's dubious.  I tried to make this work with a Headlights figure parented to a Car figure,
and at times it did seem to work but I couldn't repeat it.  (Or I could have been deluding
myself, which is always Possibility #1 in a situation like this!)

The times when it seemed to work, I had this code in the child's LightsOn parm:

        valueParm LightsOn
            {
            name LightsOn
            initValue 0
            hidden 0
            forceLimits 1
            min 0
            max 1
            trackingScale 1
            keys
                {
                static  0
                k  0  0
                }
            interpStyleLocked 0
            valueOpDeltaAdd
                ElectricCar
                BODY
                Lamps
            deltaAddDelta 1.0
            }

Note that the specific name of the parent figure is in the ERC, not just "Figure 1".

You could try something like this and see what happens.

FWIW, this sort of control definitely does work with a smart-prop as opposed to a child figure.

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