Does the IDE only allow Java versions 8 and 11 to be compiled ?
If I set the tools path to java 8 javac , it compiles in java 8.
If I set it to java 11 javac, it compiles in java 11.
If I set it to java 14 javac, it compiles in java 8 although the GetSystemProperty("java.version","") reports java 14.
Because we are using openjdk / openjfx, unless I am mistaken, these don't get updates / bug fixes. So we are basically using the version that was originally posted by yourself, when java 11 was available for use inthe IDE.
OpenJDK is updated. You can build your own package based on Java 11. You will just need to combine OpenJDK + OpenJFX in the same way as the package downloaded from here.