Allow adding folder manually by path

I'm running headless mode in aarch64. When I click on add folder to add my sources to library,  it just shows a blank pop-up. The following error is logged: 

```

20250824 06:56:22 [qtp1368251707-46] WARN o.e.j.server.handler.ContextHandler - Unimplemented getRequestCharacterEncoding() - use org.eclipse.jetty.servlet.ServletContextHandler

```

I'm assuming it's trying to open up a file chooser using native call on the OS it's being run from. Would be nice to be able to add folders using absolute paths.