Unable to add external jar to work with LSP

I'm using Visual Studio Code for a Java project without build tools (e.g., Maven or Gradle). I've added JAR files using the java.project.referencedLibraries setting. While auto-completion and documentation pop-ups work, there is no proper syntax highlighting (LSP-based) for the referenced classes and methods within the JARs.

Steps to Reproduce:

1. Open a Java project in VS Code.
2. Add JAR files directly to the java.project.referencedLibraries setting.
3. Use a class or method from the JAR in your code.

Expected Behavior:

LSP features should include syntax highlighting for classes and methods from the JARs, in addition to auto-completion and documentation pop-ups.

Actual Behavior:

While auto-completion and documentation pop-ups work, syntax highlighting does not apply for the JAR dependencies.

Screenshot:

• Referencing the JAR:
  
• Missing syntax highlighting:
  

Additional Context:

This issue occurs in a setup without Maven or Gradle. Are there additional configurations required to enable full syntax highlighting for JAR dependencies?

Reproduce the issue in VS Code using a Java project without Maven or Gradle and the java.project.referencedLibraries setting, then trace how referenced JAR classes are handled for syntax highlighting. Done means classes and methods from those JARs receive syntax highlighting while completion and documentation continue to work.