@Florentin I had been wondering this too, and although it feels hacky, it works. I used the Vue devtools to inspect the tree instance and you can see that the filtered nodes are in the tree’s refs.
I’ve built on your codepen example to spit out the node names, you should be able to adjust to your needs from there (I attached it to the input function of q-input, so try clearing then typing in and you’ll see the selected nodes at the top.