In order to find that feature, you'll need a flashlight that emits anti-photons that go back in time. Yes, we removed the Java GUI Builder in v11. The comments you are seeing are something we missed when we took out the feature.
The GUI Builder was an interesting feature, but it had several problems that we didn't feel we had time to correct. Also, it didn't seem to be as relevant as other features we were working on. Fewer Java programmers are using Swing now than when we started the feature.
Also, our customers tend to be the kind of power programmers who prefer to write the code themselves. It's a real challenge in a product like that to get it to spit out the kind of code you would write yourself. After I built something with the GUI Builder, I would typically go back and rename variables. Also, it generated code in a very linear fashion, rather than grouping related statements together. So if I had a set of buttons in a container, like GridBag, and I came back later to add another button, that button would be placed at the bottom of the file rather than with the other buttons. Overall, an editor like SlickEdit allows me to write the code much faster than I could by dragging things around graphically.
So, we had to make a tough choice about whether to invest more time in addressing the problems or building something that we felt would appeal to a larger number of our users. These are very difficult decisions, and somebody is always going to be disappointed we didn't choose to work on their favorite item. I hope that's not the case with you and the GUI Builder.