Sadly no 
. I tested it just now, specifically cleared the textblocks default text, saved, then reconnected the PreConstruct method which sets the text from a text property. The text property holds the placeholder value. I restart the game and it simply says “Placeholder”. Then I reload the button asset and it gets the correct value. The correct value is set by a parent UserWidget which holds a list of buttons, there for each button the text property is set to a localized value on the editor panel. Crazy right? It’s not even everywhere it’s just random if it happens on a certain UserWidget both game and editor. Once it happens it stays.
It’s not some weird hidden logic this happens on 100% blueprint widgets directly inheriting from UUserWidget