It seems to be missing, not sure if it is by design. However you can overlay the js file for the property predicate and add the functionality to the prediacte - /libs/dam/gui/coral/components/admin/customsearch/searchpredicates/propertypredicate/clientlibs/propertypredicate.js
Basically you would need to add a method to add/update the tag upon pressing of Enter and then submit the form. Again you would need to remove the tag when the property is cleared. You can reference /libs/dam/gui/coral/components/admin/customsearch/searchpredicates/pathbrowserpredicate/clientlibs/pathbrowserpredicate/js/pathbrowserpredicate.js to see how it is done, the handling for both the predicates would be very similar. The code is pretty self explanatory.