try it this way:
if (Faceplate.Parent.Properties.Min.Tag == "") { let numMin = Faceplate.Properties.Min2; } else { let numMin = Tags("Min").Read(); }
"Min" ist the name of the tag in the faceplates Tag interface you want to check if it is connected and use when it is connected
"Min2" is the name of a property in the faceplates Property interface which is to be used in case that the tag is not connected.