Thanks! It works and I’m able to choose the new filter in the alphabetical filter menu.
However, as I mentioned above, a drop down list is what I want, and I changed the XML property to <EnumerationDomain with several Entry as Plugin_HowTo#Drop down list describes. As a result, the property DiscreteTimeStepValue was displayed without a dropdown list, nor even any input, just like this:
Is the GUI parameter EnumerationDomain deprecated or it won’t work in this case?