Hi @l3gi0n I know that you mean. I vaguely remember not being able to succeed when trying to pass the browser command with URL substitution via
%s (just like you are attempting to do), but I finally managed to set it up on Ubuntu by creating a custom “executable” (a single-line bash script that takes the URL and starts Chrome with
--app=URL flag), adding it to my PATH and setting the browser to this executable. I think it should be possible to set it up on Windows too, but the details will differ.
As for JupyterLab 3.x, please note that there was a transition to
jupyter-server and associated changes to the file (
LabApp etc); see the docs for TLDR or my longer answer on SO if you are interested in more details.