Can someone explain why global flatpaks are installed in /var/lib and not /opt or /usr/local?

Fantastic, Linux needs tools like this for users who need to make occasional changes and inspect systemd.

For inspiration, I would suggest you also look at LaunchControl, which is a GUI tool to administer launchd on macOS.

With the Reboot Into Selected, will this modify the next boot only without changing the default?

I miss the KDE 3.x crystal theme

Thanks for the suggestion I’ll follow it up!