Typically, no additional resistor is needed in series with the diode in the backup OR‑ing path. The diode itself prevents reverse conduction and provides the needed isolation between the bus supply and the net rail. Adding a resistor could introduce an extra voltage drop that might affect the voltage presented at the net rail.

Of course, if you encounter issues like inrush current or need further current limiting under specific transient conditions, then you might consider a very low-value resistor. However, in most designs, connecting the diode directly is standard practice.

Would you like further clarification on any part of the design?

Yes, for a complete simulation it's a good idea to add a load to the net rail. A load resistor (or any representative load element) will help you analyze how the circuit behaves under current draw conditions, including the voltage delivered to the load and any potential voltage drops in your OR-ing path.

Would you like any recommendations on load resistor values for typical simulations?