You can refer OOTB(out of the box) UI Gallery example i.e. pxFeatureDetails section under the class Data-UIGallery-Features-Events to understand the usage of hidden text property. Here, a hidden text is created for .pyColor property(of property type as 'Text' and UI control as pxTextInput).
In this section(pxFeatureDetails), there are button configured(red, green, blue and reset). Action set(click-Set Value) is configured on these button to set the value hidden text property(.pyColor).