I use KMM on various systems and I sync my KMM data file in real time with Syncthing. This can cause problems if I forget that it's open on one system when I open it on a different system.

To get around this, I run KMM using a bash script that checks for the presence of a lock file named "MyFileName.kmy.lock". 

If the lock file is present, my script reads the hostname from the lock file and uses zenity to open a dialog box telling me that KMM is already open on the hostname stored in the lock file and it does NOT run KMM.

If the lock file is not present, my script creates the lock file and copies the hostname into the lock file. When KMM closes, the lock file is removed.

It would be nice if this functionality was all handled by KMM. It could be turned on and off in the KMM settings since some people may prefer it the way it is today.