KDE groups Chromium-based browser windows by app_id. Launching a second
profile with --profile-directory=… doesn't help — the browser's IPC merges
everything into one process, so all windows share the same app_id and KDE
has no choice but to group them under one icon.
The fix is to give each profile its own --user-data-dir, which forces
fully independent process trees. Then --class and StartupWMClass start
working, and KDE treats the profiles as separate apps that each group their