Add button onto content panel
In properties panel mouse over "Text" property. Click on gear and choose "Replace with Internatiolization String". Type "text".
Add file "some.properties" Preview -> Internatiolizaton -> Set Resource with "text=helloWorld"
Open file "some.properties" in external text editor and change value of property "text" from "helloWorld" to "hello".
Save file. You should see that button in SceneBuilder change text to "hello"
Rename Properties file. You should get warning "Refreshed untitled" in Scene Builder and button change text to "%text. But there is no warning and button has "hello" text