Please find attached an example of a diode over voltage issue that we recently ran into. We have a technology in which the Nwell-Substrate diode (dNw in the attached PNG) reverse voltage may not exceed 5V. Is it possible that InsightEDA can screen a design CDL for this rule? In other words, is there a diode-over-voltage script like there currently is the resistor-over-voltage script in InsightAnalyzer?

If I understand you correctly, the answer is a simple "yes". I've attached a screen capture of the device parameters for MOSFETs, showing a mode for enhanced definitions used in voltage applications (from the Settings / Project / Flow = Voltage). In this mode, the parameters are expanded to allow definitions for asymmetric device requirements. The columns to the right are for Vgb / Vdb / Vsb. These parameters are normally taken from the Vgs / Vds values (to the left), which are commonly used. But in some cases as you say, the requirements for Bulk node vs the others might be different. Well, the same notion applies to gate, for example Vgs-max is different from Vgd-max.

Then it's a matter of running the built-in checks for V-gate-over and V-sd-over (bulk terminals are checked inherently as part of such MOSFET checking).

So I believe this is what you need?

If, on the other hand, you need something specific to diodes themselves (perhaps diodes within wrapper cells around MOSFET have been preserved and you want to enforce rules on the diodes), please do let me know if I've misunderstood.