- create a new maven project
- add the entry <netbeans.hint.jdkPlatform>JDK_13</netbeans.hint.jdkPlatform> to the properties in the pom.xml
- open the project properties dialog go to Build -> Compile
- Switch "Java Platform" to the entry that is marked "(Default)".
- Acknowledge the change with OK
- Check pom.xml
Why not remove the property from the POM? (override the value from a parent pom?)
Not sure if I understand what you're asking, but if it is: why don't you remove the property from the POM? Then, yes, it doesn't make sense to specify @@DEFAULT@@ as the value, but if NetBeans writes it to the POM, it should at least do so without typos. And ideally it shouldn't write it to the POM at all, but that's an issue of its own
How is this story about backwards compatibility?
Imho this is a negligible issue. At worst, people will get an Unresolved project problem saying No such Java Platform: @@DEFAU:T@@, upon which they'll select a Java Platform of their choosing in the settings and that's it. But I doubt this will impact many users at all.