so you've got a process that you want to keep running. you might have it in a tmux or screen session. let's use systemd user units to manage it!
mkdir -p ~/.config/systemd/user/
[Unit] Description=foo [Service] ExecStart=/bin/bash -c "while true do; echo hi; done" [Install] WantedBy=default.target
systemctl --user enable --now my-new-service.service
this allows your user units to run even when you're not logged in.
you can now use
systemctl --user to manage your daemonized process.