It looks like the unit names are deeply buried in LabVIEW resource files and therefore difficult to modify without quite a bit of hackery. But there's an easy workaround: use dimensionless numerics for your H2O pressure values. When you need to feed them into calculations or indicators set to any other units (such as Pascals or atmospheres), use the Convert Unit node from the Numeric >> Conversions palette in series with an Expression node containing the appropriate multiplier.
