zoom (narrow) in and out of specific sub-object

According to https://github.com/PaulJuliusMartinez/jless/issues/80#issuecomment-1099492349, `fx` has (or at least had) a feature for zooming into a sub-object, so that you only see that part of the tree. In other words, that path temporarily becomes the new root, and you can "unzoom" (exit) back to the full object afterwards. However I can't find that feature in https://fx.wtf/key-bindings or anywhere else. Was it removed? This would be a super helpful feature, especially for large objects!