possible solution ...
Just a rough concept at this point .... don't have a schematic ....:
Consider a two input unity feedback summing amplifier.
One of the two inputs is held constant at +12 Vdc... a voltage divider from the 24 V psu.
The other input to the amplifier is connected to the variable voltage output of the PLC, and sees a range of voltage from + 5 Vdc for one direction, to 0 Vdc for the stop condition, to - 5 Vdc for the opposite rotation direction.
If the output of the summing amplifier yields a negative voltage, then send the resultant signal through a unity feedback amplifier, to achieve the correct polarity.
If this idea meets your basic expectations, you would want to get a circuit simulation, or a breadboard confirmation, including op amp selection, appropriate components, power supplies, and layout.
Additional considerations:
.... estimate the max current necessary to operate the valve. From your previous diagram, that value would be 20 mA.
.... Is the zero voltage control position on the valve critical? Do you need to have absolute zero volts, or is approximately zero close enough, to prevent problems such as dithering, in the stop position.